Electronics for detection of a condition of tissue

ABSTRACT

Apparatus are provided for monitoring a condition of a tissue based on a measurement of an electrical property of the tissue. In an example, the electrical property of the tissue is performed using an apparatus disposed above the tissue, where the apparatus includes at least two conductive structures, each having a non-linear configuration, where the at least two conductive structures are disposed substantially parallel to each other. In another example, the electrical property of the tissue is performed using an apparatus disposed above the tissue, where the apparatus includes at least one inductor structure.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/603,290, filed Sep. 4, 2012, now allowed, which claims priority toand the benefit of U.S. provisional application Ser. No. 61/530,283,filed Sep. 1, 2011, U.S. provisional application Ser. No. 61/540,421,filed Sep. 28, 2011, U.S. provisional application Ser. No. 61/541,762,filed Sep. 30, 2011, U.S. provisional application Ser. No. 61/649,035,filed May 18, 2012, and U.S. provisional application Ser. No.61/681,545, filed Aug. 9, 2012, each of which is hereby incorporated byreference herein in its entirety.

BACKGROUND

Effort is being made to develop electronics for application in measuringelectrical properties of biological tissue. For example, effort is beingmade to develop electronics that can be applied to measure a propertysuch as tissue hydration level.

Tissue hydration is the process of absorbing and retaining water inbiological tissues. In humans, a significant drop in tissue hydrationcan lead to dehydration and may trigger other serious medicalconditions. Dehydration may result from loss of water itself, loss ofelectrolytes, and/or a loss of blood plasma. Previous techniques formonitoring tissue hydration have applied, e.g., an ultrasonic hydrationmonitor that employs ultrasound velocity to calculate hydration level.The ultrasound hydration monitor is generally attached to tissue such asmuscles. The device generally uses a rigid frame to maintain a constantdistance between an ultrasound transducer and a receiver.

The use of electronics in such medical-related applications can behampered by the boxy, rigid way that much electronics are designed andpackaged. Biological tissue is mainly soft, pliable and curved. Bycontrast, boxy, rigid electronics can be hard and angular, which couldaffect the measurement of tissue.

SUMMARY

In view of the foregoing, it is recognized and appreciated herein thatboth sufficient comfort and accuracy are desirable attributes oftechniques for monitoring tissue condition.

Various examples described herein are directed generally to tissuecondition monitoring methods, apparatus, and systems applicable to bothconsumer and military markets, which can provide real-time feedback aswell as portability. The tissue condition can be state of hydration ordisease state. In some examples, the methods, apparatus and systems arebased at least in part on measuring electrical properties of the skinand underlying tissue.

An example apparatus is described for monitoring a condition of atissue. The apparatus includes at least two conductive structuresdisposed above the tissue, where each of the at least two conductivestructures has a non-linear configuration, and where the at least twoconductive structures are disposed substantially parallel to each other;at least two brace structures, each disposed substantiallyperpendicularly to the orientation of the at least two parallelconductive structures, and each being in electrical communication withat least one of the at least two parallel conductive structures; and atleast one spacer structure that is physically coupled at each end to aportion of each of the at least two brace structures, such that asubstantially uniform separation is maintained between the at least twobrace structures. A measure of an electrical property of the tissueusing the apparatus provides an indication of the condition of thetissue.

The condition of the tissue can be a hydration state of the tissue, avolume of sweat lost, a mechanical property of the tissue, a diseasestate of the tissue, or a level of SPF protection of the tissue.

For the example apparatus, each of the at least two conductivestructures can have a zig-zag conformation, a serpentine configuration,or a rippled configuration.

Each of the at least two brace structures can be formed from aconductive material, and where each of the at least two brace structureselectrically links the at least two conductive structures to an externalcircuit.

The at least two brace structures can be configured to maintain aseparation of neighboring conductive structures of the at least twoconductive structures to a substantially uniform value.

Each of the at least one spacer structure can be disposed substantiallyparallel to a principal direction of the at least two parallelconductive structures.

Each of the at least two brace structure can be in electricalcommunication with at least one electrical contact of the apparatus,where the at least one electrical contact is in electrical communicationwith at least one of a power source, a wireless receiver, a wirelesstransmitter, a wireless transceiver, and a temperature sensor.

The example apparatus can include a plurality of cross-link structuresdisposed between neighboring conductive structures, each cross-linkstructure of the plurality of cross-link structures being formed from adielectric material.

The example apparatus can include an encapsulation layer disposed overat least a portion of the at least two conductive structures. In anexample, portions of the encapsulation layer comprise an adhesive, wherethe adhesive attaches the portions of the encapsulation layer to thetissue.

The apparatus can include a plurality of cross-link structures disposedbetween neighboring conductive structures, each cross-link structure ofthe plurality of cross-link structures being formed from the samematerial as the encapsulation layer.

In an example, the encapsulation layer is a polymer. In another example,the polymer is a polyimide.

The example apparatus can include a backing layer in physicalcommunication with at least a portion of the at least two conductivestructures, where the backing layer is a polymer.

The apparatus in this example implementation can include an ultrasoundapparatus, where the ultrasound apparatus provides a measure of anelectrical property of the tissue. The ultrasound an apparatus caninclude an ultrasound generator disposed proximate to a first portion ofthe tissue of interest, where the ultrasound generator comprises apiezoelectric crystal, where the ultrasound generator directs ultrasoundwaves at a portion of the tissue; and an ultrasound receiver disposedproximate to a second portion of the tissue of interest that isdifferent from the first portion. The ultrasound receiver provides ameasure of ultrasound waves arriving at the second portion of thetissue. The measure of ultrasound waves arriving at the second portionof the tissue provides an indication of the condition of the tissue.

A system for monitoring a condition of a tissue is also provided. Theexample system includes at least one of any of the apparatus of thisexample implementation and at least one other component. The at leastone other component can be at least one of a battery, a transmitter, atransceiver, a memory, a radio-frequency identification (RFID) chip, aprocessing unit, an analog sensing block, a UVA sensor, a UVB sensor,and a temperature sensor.

A method for monitoring a condition of a tissue is also provided. Themethod can include receiving data indicative of an electricalmeasurement of the tissue, where the electrical measurement is performedusing at least one apparatus described herein; and analyzing the datausing at least one processor unit, where the analysis provides anindication of the condition of the tissue.

In an example, the analyzing the data can include applying an effectivecircuit model to the data, where a value of a parameter of the modelprovides the indication of the condition of the tissue.

In another example, the analyzing the data can include comparing thedata to a calibration standard, where the comparing provides theindication of the condition of the tissue. The calibration standard caninclude a correlation between values of electrical measurement and theindication of the condition of the tissue.

Another example apparatus for monitoring a condition of a tissue isdescribed. The apparatus includes a plurality of conductive structuresdisposed above the tissue, where each of the plurality of conductivestructures has a non-linear configuration, and where the plurality ofconductive structures are disposed substantially parallel to each otherin an interdigitated configuration; at least two brace structures, eachdisposed substantially perpendicularly to the orientation of the atleast two parallel conductive structures, and each brace structure beingin electrical communication with at least one of the plurality ofconductive structures; and at least one spacer structure that isphysically coupled at each end to a portion of each of the at least twobrace structures, such that a substantially uniform separation ismaintained between the at least two brace structures. A measure of anelectrical property of the tissue using the apparatus provides anindication of the condition of the tissue.

For this example apparatus, the condition of the tissue can be ahydration state of the tissue, a volume of sweat lost, a mechanicalproperty of the tissue, a disease state of the tissue, or a level of SPFprotection of the tissue.

Each of the plurality of conductive structures can have a zig-zagconformation, a serpentine configuration, or a rippled configuration.

Each of the at least two brace structures can be formed from aconductive material, and where each of the at least two brace structureselectrically links the plurality of conductive structures to an externalcircuit.

The at least two brace structures are configured to maintain aseparation of neighboring conductive structures of the plurality ofconductive structures to a substantially uniform value.

Each of the at least one spacer structure can be disposed substantiallyparallel to a principal direction of the at least two parallelconductive structures.

Each of the at least two brace structure can be in electricalcommunication with at least one electrical contact of the apparatus,where the at least one electrical contact is in electrical communicationwith at least one of a power source, a wireless receiver, a wirelesstransmitter, a wireless transceiver, and a temperature sensor.

In an example, the apparatus can include a plurality of cross-linkstructures disposed between neighboring conductive structures, eachcross-link structure of the plurality of cross-link structures beingformed from a dielectric material.

The example apparatus of this implementation can include anencapsulation layer disposed over at least a portion of the plurality ofconductive structures. Portions of the encapsulation layer can includean adhesive, where the adhesive attaches the portions of theencapsulation layer to the tissue.

The example apparatus can include a plurality of cross-link structuresdisposed between neighboring conductive structures, each cross-linkstructure of the plurality of cross-link structures being formed fromthe same material as the encapsulation layer.

The encapsulation layer can be a polymer. In an example, the polymer isa polyimide.

The example apparatus can include a backing layer in physicalcommunication with at least a portion of the plurality of conductivestructures, where the backing layer is a polymer.

The apparatus in this example implementation can include an ultrasoundapparatus, where the ultrasound apparatus provides a measure of anelectrical property of the tissue. The ultrasound an apparatus caninclude an ultrasound generator disposed proximate to a first portion ofthe tissue of interest, where the ultrasound generator comprises apiezoelectric crystal, where the ultrasound generator directs ultrasoundwaves at a portion of the tissue; and an ultrasound receiver disposedproximate to a second portion of the tissue of interest that isdifferent from the first portion. The ultrasound receiver provides ameasure of ultrasound waves arriving at the second portion of thetissue. The measure of ultrasound waves arriving at the second portionof the tissue provides an indication of the condition of the tissue.

A system for monitoring a condition of a tissue is also provided. Theexample system includes at least one apparatus of of this exampleimplementation and at least one other component. The at least one othercomponent can be at least one of a battery, a transmitter, atransceiver, a memory, a radio-frequency identification (RFID) chip, aprocessing unit, an analog sensing block, a UVA sensor, a UVB sensor,and a temperature sensor.

A method for monitoring a condition of a tissue is also provided. Themethod includes receiving data indicative of an electrical measurementof the tissue, where the electrical measurement is performed using atleast one of the apparatus according tto this example implementation andanalyzing the data using at least one processor unit, where the analysisprovides an indication of the condition of the tissue.

In an example, the analyzing the data can include applying an effectivecircuit model to the data, and where a value of a parameter of the modelprovides the indication of the condition of the tissue.

In another example, the analyzing the data can include comparing thedata to a calibration standard, and where the comparing provides theindication of the condition of the tissue.

The calibration standard can include a correlation between values ofelectrical measurement and the indication of the condition of thetissue.

Another example apparatus for monitoring a condition of a tissue is alsoprovided. The apparatus includes at least two conductive structuresdisposed above the tissue and running substantially parallel to eachother along substantially an entire length of the conductive structures,where each of the conductive structures has a curved configuration; andat least two contact structures, each being in electrical communicationwith at least one of the at least two parallel conductive structures. Ameasure of an electrical property of the tissue using the apparatusprovides a measure of the condition of the tissue.

In this example implementation, the condition of the tissue can be ahydration state of the tissue, a volume of sweat lost, a mechanicalproperty of the tissue, a disease state of the tissue, or a level of SPFprotection of the tissue.

Each of the plurality of conductive structures can have a zig-zagconformation, a serpentine configuration, or a rippled configuration.

Each of the at least two conductive structures is configured to maintaina separation of neighboring conductive structures of the at least twoconductive structures to a substantially uniform value of distance.

Each of the at least two contact structures electrically links the atleast two conductive structures to an external circuit.

Each of the at least two contact structures can be in electricalcommunication with at least one of a power source, a wireless receiver,a wireless transmitter, a wireless transceiver, and a temperaturesensor.

In an example, the apparatus can include an encapsulation layer disposedover at least a portion of the at least two conductive structures.Portions of the encapsulation layer can include an adhesive, where theadhesive attaches the portions of the encapsulation layer to the tissue.

The encapsulation layer can be a polymer. In an example, the polymer isa polyimide.

The example apparatus according to this implementation can include atleast one cross-link structure coupled at each end thereof to a portionof each of the least two conductive structures.

Each of the at least one cross-link structure can be disposedsubstantially perpendicularly to the portion of the at least twoparallel conductive structures.

The example apparatus can include a plurality of cross-link structuresdisposed between the at least two conductive structures, each cross-linkstructure of the plurality of cross-link structures being formed from adielectric material.

The example apparatus can include a plurality of cross-link structuresdisposed between neighboring conductive structures, each cross-linkstructure of the plurality of cross-link structures being formed fromthe same material as the encapsulation layer.

In an example, the encapsulation layer is a polymer. The polymer can bea polyimide.

The example apparatus can include a backing layer in physicalcommunication with at least a portion of the at least two conductivestructures, where the backing layer is a polymer.

The apparatus in this example implementation can include an ultrasoundapparatus, where the ultrasound apparatus provides a measure of anelectrical property of the tissue. The ultrasound an apparatus caninclude an ultrasound generator disposed proximate to a first portion ofthe tissue of interest, where the ultrasound generator comprises apiezoelectric crystal, where the ultrasound generator directs ultrasoundwaves at a portion of the tissue; and an ultrasound receiver disposedproximate to a second portion of the tissue of interest that isdifferent from the first portion. The ultrasound receiver provides ameasure of ultrasound waves arriving at the second portion of thetissue. The measure of ultrasound waves arriving at the second portionof the tissue provides an indication of the condition of the tissue.

A system is also provided for monitoring a condition of a tissue, wherethe system includes at least one apparatus of this exampleimplementation and at least one other component. The at least one othercomponent can be at least one of a battery, a transmitter, atransceiver, a memory, a radio-frequency identification (RFID) chip, aprocessing unit, an analog sensing block, a UVA sensor, a UVB sensor,and a temperature sensor.

A method for monitoring a condition of a tissue is also provided. Themethod includes receiving data indicative of an electrical measurementof the tissue, where the electrical measurement is performed using atleast one apparatus of this example implementation and analyzing thedata using at least one processor unit, where the analysis provides anindication of the condition of the tissue.

The analyzing the data can include applying an effective circuit modelto the data, and where a value of a parameter of the model provides theindication of the condition of the tissue.

The analyzing the data can include comparing the data to a calibrationstandard, and where the comparing provides the indication of thecondition of the tissue.

The calibration standard can include a correlation between values ofelectrical measurement and the indication of the condition of thetissue.

Another apparatus for monitoring a condition of a tissue is provided.The apparatus includes a substrate disposed above the tissue, where thesubstrate is formed from a material that changes a state with a changein the condition of the tissue, and at least one first inductorstructure disposed above the substrate, where at least one of anelectrical property and a physical property of the at least one firstinductor structure changes with a change in the condition of thesubstrate. A measure of the electrical property or the physical propertyof the at least one first inductor structure provides an indication ofthe condition of the tissue.

The condition of the tissue can be a hydration state of the tissue, avolume of sweat lost, a mechanical property of the tissue, a diseasestate of the tissue, or a level of SPF protection of the tissue.

In an example, the first inductor structure can be a spiral coilstructure, a cylindrical coil structure, or a toroidal structure.

In an example, the apparatus can include a reader, where the readercomprises at least one second inductor structure, where a measure of achange in an electrical property of the at least one second inductorstructure brought in proximity to the at least one first inductorstructure provides the measure of the electrical property of the atleast one first inductor structure.

In an example, the second inductor structure is the same configurationas the first inductor structure.

In an example, the first inductor structure and the second inductorstructure are a spiral coil structure, a cylindrical coil structure, ora toroidal structure.

The electrical property measured can be a magnetic flux density from theat least one first inductor structure.

In an example, the apparatus includes an encapsulation layer disposedover at least a portion of the at least one first inductor structure.The encapsulation layer can be a polymer.

In an example, portions of the polymer can include an adhesive, wherethe adhesive attaches the portions of the polymer to the tissue.

In an example, the can include a separator layer disposed between the atleast one inductor structure and the substrate, where the separatorlayer is a non-conductive material.

The separator layer can be formed from a polymer.

The apparatus in this example implementation can include an ultrasoundapparatus, where the ultrasound apparatus provides a measure of anelectrical property of the tissue. The ultrasound an apparatus caninclude an ultrasound generator disposed proximate to a first portion ofthe tissue of interest, where the ultrasound generator comprises apiezoelectric crystal, where the ultrasound generator directs ultrasoundwaves at a portion of the tissue; and an ultrasound receiver disposedproximate to a second portion of the tissue of interest that isdifferent from the first portion. The ultrasound receiver provides ameasure of ultrasound waves arriving at the second portion of thetissue. The measure of ultrasound waves arriving at the second portionof the tissue provides an indication of the condition of the tissue.

A system is also for monitoring a condition of a tissue. The systemincludes at least one apparatus of this example implementation, and atleast one other component. The at least one other component is at leastone of a battery, a transmitter, a transceiver, a memory, aradio-frequency identification (RFID) chip, a processing unit, an analogsensing block, a UVA sensor, a UVB sensor, and a temperature sensor.

A method is also provided for monitoring a condition of a tissue. Themethod includes receiving data indicative of an electrical measurementof the tissue, where the electrical measurement is performed using atleast one apparatus of this example implementation, and analyzing thedata using at least one processor unit, where the analysis provides anindication of the condition of the tissue.

The analyzing the data can include applying an effective circuit modelto the data, and where a value of a parameter of the model provides theindication of the condition of the tissue.

The analyzing the data can include comparing the data to a calibrationstandard, and where the comparing provides the indication of thecondition of the tissue.

The calibration standard can include a correlation between values ofelectrical measurement and the indication of the condition of thetissue.

The following publications, patents, and patent applications are herebyincorporated herein by reference in their entirety:

-   Kim et al., “Stretchable and Foldable Silicon Integrated Circuits,”    Science Express, Mar. 27, 2008, 10.1126/science.1154367;-   Ko et al., “A Hemispherical Electronic Eye Camera Based on    Compressible Silicon Optoelectronics,” Nature, Aug. 7, 2008, vol.    454, pp. 748-753;-   Kim et al., “Complementary Metal Oxide Silicon Integrated Circuits    Incorporating Monolithically Integrated Stretchable Wavy    Interconnects,” Applied Physics Letters, Jul. 31, 2008, vol. 93,    044102;-   Kim et al., “Materials and Noncoplanar Mesh Designs for Integrated    Circuits with Linear Elastic Responses to Extreme Mechanical    Deformations,” PNAS, Dec. 2, 2008, vol. 105, no. 48, pp.    18675-18680;-   Meitl et al., “Transfer Printing by Kinetic Control of Adhesion to    an Elastomeric Stamp,” Nature Materials, January, 2006, vol. 5, pp.    33-38;-   U.S. patent application publication no. 2010 0002402-A1, published    Jan. 7, 2010, filed Mar. 5, 2009, and entitled “STRETCHABLE AND    FOLDABLE ELECTRONIC DEVICES;”-   U.S. patent application publication no. 2010 0087782-A1, published    Apr. 8, 2010, filed Oct. 7, 2009, and entitled “CATHETER BALLOON    HAVING STRETCHABLE INTEGRATED CIRCUITRY AND SENSOR ARRAY;”-   U.S. patent application publication no. 2010 0116526-A1, published    May 13, 2010, filed Nov. 12, 2009, and entitled “EXTREMELY    STRETCHABLE ELECTRONICS;”-   U.S. patent application publication no. 2010 0178722-A1, published    Jul. 15, 2010, filed Jan. 12, 2010, and entitled “METHODS AND    APPLICATIONS OF NON-PLANAR IMAGING ARRAYS;”-   U.S. patent application publication no. 2010 027119-A1, published    Oct. 28, 2010, filed Nov. 24, 2009, and entitled “SYSTEMS, DEVICES,    AND METHODS UTILIZING STRETCHABLE ELECTRONICS TO MEASURE TIRE OR    ROAD SURFACE CONDITIONS;”-   PCT Patent Application publication no. WO2011/084709, published Jul.    14, 2011, entitled “Methods and Apparatus for Conformal Sensing of    Force and/or Change in Motion;” and-   U.S. patent application publication no. 2011 0034912-A1, published    Feb. 10, 2011, filed Mar. 12, 2010, and entitled “SYSTEMS, METHODS,    AND DEVICES HAVING STRETCHABLE INTEGRATED CIRCUITRY FOR SENSING AND    DELIVERING THERAPY.”

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the subject matter disclosed herein. In particular, all combinationsof claimed subject matter appearing at the end of this disclosure arecontemplated as being part of the subject matter disclosed herein. Itshould also be appreciated that terminology explicitly employed hereinthat also may appear in any disclosure incorporated by reference shouldbe accorded a meaning most consistent with the particular conceptsdisclosed herein.

The foregoing and other aspects, examples, and features of the presentteachings can be more fully understood from the following description inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the figures, described herein,are for illustration purposes only. It is to be understood that in someinstances various aspects of the invention may be shown exaggerated orenlarged to facilitate an understanding of the invention. In thedrawings, like reference characters generally refer to like features,functionally similar and/or structurally similar elements throughout thevarious figures. The drawings are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the teachings.The drawings are not intended to limit the scope of the presentteachings in any way.

FIG. 1A shows a block diagram of an example system for monitoringcondition of a tissue, according to the principles herein.

FIG. 1B shows a block diagram of another example system for monitoringcondition of a tissue, according to the principles herein.

FIG. 2 shows examples of tissue conditions or tissue sections that maybe monitored using the example apparatus, according to the principlesherein.

FIG. 3 shows a cross-section view of an example apparatus for monitoringcondition of a tissue, according to the principles herein.

FIG. 4 shows a cross-section view of another example apparatus formonitoring condition of a tissue, according to the principles herein.

FIG. 5 shows an example apparatus that includes interdigitatedconductive structures, according to the principles herein.

FIG. 6 is an illustration of the example apparatus of FIG. 5, withselected portions magnified, according to the principles herein.

FIG. 7 shows an example of an apparatus with cross-link structuresdisposed between interdigitated conductive structures, according to theprinciples herein.

FIG. 8 shows an example apparatus with curved conductive structures,according to the principles herein.

FIG. 9 shows another example apparatus with curved conductive structuresand cross-link structures, according to the principles herein.

FIG. 10 shows another example with curved conductive structures,according to the principles herein.

FIGS. 11A-11I show an example process for fabricating an exampleapparatus, according to the principles herein.

FIGS. 12A-12E show an example apparatus that includes the interdigitatedconductive structures, according to the principles herein.

FIG. 13A shows a finite element (FE) model for deformation of anapparatus, according to the principles herein.

FIG. 13B shows an apparatus that is stretched at 50% elongation,according to the principles herein.

FIGS. 14A-14B show an example apparatus having interdigitated conductivestructures in a relaxed state (FIG. 14A) and elongated by 50% (FIG.14B), according to the principles herein.

FIGS. 15A-15B show plots of the magnitude and phase, respectively, ofthe impedance change with the sweat level at selected measurementfrequencies, according to the principles herein.

FIGS. 16A-16B show performance of the example apparatus of FIGS. 14A-14Bversus impedance and capacitance, respectively, according to theprinciples herein.

FIG. 17 shows a simulation of the distance changes between theconductive structures during stretching of the substrate, according tothe principles herein.

FIG. 18 shows the simulated out-of-plane deformation while the inset toFIG. 18 shows the optical image of the stretchable interconnect,according to the principles herein.

FIG. 19A-19B show an example apparatus that include an inductorstructure, according to the principles herein.

FIG. 20 shows a system that includes an example reader including aninductor structure, according to the principles herein.

FIGS. 21-23 show quarter sections of example sensing patches, accordingto the principles herein.

FIG. 24 shows a cross-section of an example ultrasound system, accordingto the principles herein.

FIG. 25 illustrates an example operation of the example ultrasoundsystem when a voltage is applied, according to the principles herein.

FIG. 26A shows an example device mount about a bicep tissue, accordingto the principles herein.

FIG. 26B shows a cross-section of the device mount of FIG. 26A,according to the principles herein.

FIG. 27 illustrates use of a patch with a handheld device for monitoringtissue condition, according to the principles herein.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and examples of, methods and apparatus for measuringelectrical properties of tissue. It should be appreciated that variousconcepts introduced above and discussed in greater detail below may beimplemented in any of numerous ways, as the disclosed concepts are notlimited to any particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

As used herein, the term “includes” means includes but not limited to,the term “including” means including but not limited to. The term “basedon” means based at least in part on.

The apparatus and systems described herein provide technology platformsthat use ultra-thin components linked with stretchable interconnects andembedded in low modulus polymers which provide a match to biologicaltissue. The technology platform implements high-performance activecomponents in new mechanical form factors.

In non-limiting example, the technology platforms according to theprinciples described herein can be fabricated based on foundrycomplimentary metal-oxide-semiconductor (CMOS) wafers and transferred topolymer-based and/or polymer-coated carriers.

The technology platforms according to the principles herein provideapparatus and systems for on-body and in-body applications. As anon-limiting example, any of the example apparatus or systems describedherein can be mounted directly to tissue. For example, the apparatus orsystem can be skin-mounted. In any example implementation describedherein, an apparatus or system may be disposed on tissue for extendedperiods without discomfort, while facilitating continuous monitoring.For implementations inside the body, an apparatus or system describedherein may be mounted to a catheter or other equivalent instrument whichis disposed proximate to the tissue of a tissue lumen to provideelectrical information about the tissue interior. For example, thetissue lumen can be but is not limited to the lumen of the heart.

As described in greater detail below, an apparatus or system accordingto the principles described herein can be implemented for measuringelectrical properties of tissue. The apparatus or system can beconfigured to measure the electrical properties of the tissue through acapacitive-based measurement or through an inductance-based measurement.The measured electrical properties can be used as an indicator of thetissue condition. For example, the measurement of electrical propertiescan be used to monitor, e.g., the disease state of the tissue,mechanical properties of the tissue (including tissue firmness), thesweat level of the tissue (which can be related to its hydration level),or other condition of the tissue. Information from an ultrasoundmeasurement also can be used to provide information about the diseasestate of the tissue, mechanical properties of the tissue (includingtissue firmness), the sweat level of the tissue (which can be related toits hydration level), or other condition of the tissue.

An apparatus according to the principles described herein can beconfigured to measure electrical properties of the tissue through acapacitive-based measurement. An apparatus according to this exampleimplementation can include at least two conductive structures disposedabove the tissue. The capacitive-based measurement can be performed byapplying a potential across the at least two conductive structures. Theat least two conductive structures are disposed substantially parallelto each other. Each of the at least two conductive structures has anon-linear configuration (such as but not limited to a serpentineconfiguration, a zig-zag configuration, or a rippled configuration). Theapparatus also includes at least two brace structures, each disposedsubstantially perpendicularly to the orientation of the at least twoparallel conductive structures, and at least one spacer structure thatis physically coupled at each of its ends to a portion of each of the atleast two brace structures. Each of the at least two brace structures isin electrical communication with at least one of the at least twoparallel conductive structures. The at least one spacer structurefacilitates maintaining a substantially uniform separation between theat least two brace structures. A measure of the electrical property ofthe tissue using the apparatus is used to provide an indication of thecondition of the tissue according to any of the principles describedherein.

In another example implementation where the apparatus is configured tomeasure electrical properties of the tissue through a capacitive-basedmeasurement, the apparatus can include at least two conductivestructures that run substantially parallel to each other alongsubstantially an entire length of the conductive structures. Each of theconductive structures can have a curved configuration. An apparatusaccording to this example implementation also can include at least twocontact structures. Each of the at least two contact structures is inelectrical communication with at least one of the at least two parallelconductive structures. The capacitive-based measurement can be performedby applying a potential across the at least two conductive structuresusing the at least two contact structures. A measure of the electricalproperty of the tissue using the apparatus is used to provide anindication of the condition of the tissue according to any of theprinciples described herein.

An apparatus according to the principles described herein can beconfigured to measure electrical properties of the tissue through aninductance-based measurement. An apparatus according to this exampleimplementation can include a substrate disposed above the tissue,wherein the substrate is formed from a material that exhibits a changein a state with a change in tissue condition. As a non-limiting example,the substrate can be formed from a material that changes hydration statewith a change in the sweat level of the tissue (which can be related toits hydration level). The apparatus further includes at least one firstinductor structure disposed above the substrate. As non-limitingexamples, the inductor structure can be a spiral coil structure, acylindrical coil structure, or a toroidal structure. Theinductance-based measurement can be performed by applying a signal tothe at least one first inductor structure. An electrical property and/ora physical property of the at least one first inductor structure changeswith the change in a\the state of the substrate. A measure of theelectrical property or the physical property of the at least one firstinductor structure using the apparatus is used to provide an indicationof the tissue condition.

In an example implementation, any of the apparatus configured to measureelectrical properties of the tissue through a capacitance-based orinductance-based measurement may be disposed directly above the tissue.In this example, the apparatus is used to measure an electrical propertybased on the condition of the tissue in the instant of measurement. Ameasurement according to this example can be used to provide anindication of a skin hydration level.

In another example implementation any of the apparatus configured tomeasure electrical properties of the tissue through a capacitance-basedor inductance-based measurement may be disposed above the tissue with anabsorbing layer positioned between the apparatus and the tissue. In thisexample, a measurement of a change in the state of the absorbing layercan be used to provide an indication of the condition of the tissue. Forexample, an absorbing layer that can absorb sweat may be disposedbetween the tissue and the example layer. In this example, the apparatusis used to measure an electrical property based on the amount ofaccumulated sweat in the absorbing layer. That is, each subsequentmeasurement of an electrical property is based on the higher amount ofaccumulated sweat over time in the absorbing layer. This measurementbased on accumulated sweat can be related to the hydration level of thetissue. A measurement according to this example also can be used toprovide an indication of a sweat rate (i.e., an amount of sweat gatheredover an interval).

In an example, the potential applied to any of the apparatus describedherein can be a time-varying potential. That is, any of the measurementsperformed herein, including a capacitance measurement or an inductancemeasurement, can be performed by changing the potential with time. Thepotential can be changed either periodically, or as a step function fromone value of potential to another.

FIG. 1A shows a block diagram of a non-limiting example system accordingto the principles herein. The example system 100 includes at least oneapparatus 102 that can be used to provide a measurement of theelectrical properties of the tissue. The at least one apparatus 102 canbe configured as describe herein to perform a capacitive-basedmeasurement and/or an inductance-based measurement of the electricalproperties of the tissue. The system 100 includes at least one othercomponent 104 that is coupled to the at least one apparatus 102. In anexample implementation, the at least one component 104 can be configuredto supply the potential to the apparatus 102. For example, the at leastone component 104 can include a battery or any other energy storagedevice that can be used to supply the potential. In an exampleimplementation, the system 100 can include at least one component 104for providing an indication of the tissue condition based on themeasured electrical property of the tissue. In an exampleimplementation, the at least one component 104 can include at least oneprocessor unit configured for analyzing the signal from the apparatusbased on the measurement of the electrical property of the tissue. In anexample implementation, the at least one component 104 can be configuredto transmit a signal from the apparatus based on the measurement of anelectrical property of the tissue. For example, the at least onecomponent 104 can include a transmitter or a transceiver configured totransmit a signal including data measured by the apparatus measurementfrom the apparatus to a hand-held device or other computing device.Non-limiting examples of a handheld device include a smartphone, atablet, a slate, an e-reader, a digital assistant, or any otherequivalent device. As a non-limiting example, the hand-held device orother computing device can include a processor unit that is configuredfor analyzing the signal from the apparatus based on the measurement ofthe electrical property of the tissue. The at least one other component104 can be a temperature sensor.

FIG. 1B shows a block diagram of a non-limiting example system 150according another implementation of the principles herein. The examplesystem 150 includes at least one apparatus 102 that can be used toperform a measurement of the electrical properties of the tissue,including a capacitive-based measurement and/or an inductance-basedmeasurement. In the non-limiting example of FIG. 1B, the at least oneother component 104 includes an analog sensing block 152 that is coupledto the at least one apparatus 102 and at least one processor unit 154that is coupled to the analog sensing block 152. The at least one othercomponent 104 includes a memory 156. For example, the memory 156 can bea non-volatile memory. As a non-limiting example, the memory 156 can bemounted as a portion of a RFID chip. The at least one other component104 also includes a transmitter or transceiver 158. The transmitter ortransceiver 158 can be used to transmit data from the apparatus 102 to ahandheld device or other computing device (e.g., for further analysis).The example system 150 of FIG. 1B also includes a battery 160 and acharge regulator 162 coupled to battery 160. The charge regulator 162and battery 160 are coupled to the processor unit 154 and memory 156.

A non-limiting example use of system 150 is as follows. Battery 160provides power for the apparatus 102 to perform the measurements. Theprocessor unit 154 activates periodically, stimulates the analog sensingblock 152, which conditions the signal and delivers it to an A/D port onthe processor unit 154. The data from apparatus 102 is stored in memory156. In an example, when a near-field communication (NFC)-enabledhandheld device is brought into proximity with the system 150, data istransferred to the handheld device, where it is interpreted byapplication software of the handheld device. The data logging and datatransfer can be asynchronous. For example, data logging can occur eachminute while data transfer may occur episodically.

In a non-limiting example, a system according to the principles hereincan be configured as a self-contained tissue-based system with power andwireless communication for monitoring the condition of the tissue (suchas but not limited to monitoring the sweat level of the tissue (whichcan be related to its hydration level) and/or the disease of thetissue).

In a non-limiting example, the system 100 or system 150 can be mountedon a backing, such as but not limited to a patch. The backing isdisposed over the tissue to be measured.

In a non-limited example, system 100, system 150 or any f the apparatusdescribed herein may be covered at least in part by an excapsulationlayer. The encapsulation layer can be formed from a polymer-basedmaterial, such as but not limited to a polyimide. In an example, thethickness of the encapsulation layer can be configured such that any ofthe systems or apparatus according to the principles herein lies at aneutral mechanical plane (NMP) or neutral mechanical surface (NMS) ofthe system or apparatus. The NMP or NMS lies at the position through thethickness of the device layers for the system or apparatus where anyapplied strains are minimized or substantially zero. The location of theNMP or NMS can be changed relative to the structure of the system orapparatus through introduction of materials that aid in strain isolationin the components of the system or apparatus that are used to performthe electrical measurements of the tissue. For example, the thickness ofencapsulating material disposed over the system or apparatus describedherein may be modified (i.e., decreased or increased) to depress thesystem or apparatus relative to the overall system or apparatusthickness, which can vary the position of the NMP or NMS relative to thesystem or apparatus. In another example, the type of encapsulating,including any differences in the elastic (Young's) modulus of theencapsulating material.

An apparatus or system according to the principles described herein canbe used to monitor tissue condition in conjunction with a wide range ofon-body sensors. Non-limiting examples of tissue conditions that may bemeasured using one or more of the apparatus described herein are shownin FIG. 2. For example, an apparatus or system herein can include atleast one UV sensor configured for measuring an amount of UV exposure ofthe tissue. As another example, an apparatus herein can be configured toinclude at least one temperature sensor for measuring the temperature ofthe tissue.

The apparatus and systems of the technology platform described hereinsupport conformal on-body electronics that can be used to log sensordata at very low power levels over extended periods, while providingwireless communication with external computing devices (includinghandheld devices).

For example, the technology platform described herein support conformalon-body electronics that can be used to monitor sweat rate of the body(which can be related to its hydration level). The human autonomicnervous system provides relatively slow feedback about fluid loss. Ahydration sensor that can provide real-time updates on fluid loss couldallow athletes to extend their performance period while minimizingsubsequent ill-effects and speeding recovery. In a non-limiting example,a system or apparatus described herein can be configured as a hydrationsensor that records the hydration level of a substrate material thatchanges hydration state with change in hydration of the tissue. Thesubstrate material can be a soft absorbing material that collects sweatfrom the skin, and transmits the data of measurement to an externalcomputing device (including a handheld device).

Capacitance-Impedance-Based Measurements

In a non-limiting example, skin hydration can be one of the majorphysiological responses for evaluation of dermatology, effectiveness ofmedical therapies, and cosmetology. The amount of sweat generated canprovide an indication of a person's change in overall hydration level.It also can be used to provide an indication of a person's overallhydration level.

Sweat is brought to the surface of the skin by pores formed as channelsthat go through the skin from deeper levels. Sweating can be affectedover a matter of minutes by, e.g., heat/cold or exercise/rest. Skinhydration is the water content inside the top layer of skin (the stratumcorneum), and can changes over a period of days to weeks depending on,e.g., the overall body hydration, or skin treatment.

The skin hydration level can be determined by direct electricalmeasurements of impedance-capacitance (RC measurement), or by indirectmeasurements of the skin's mechanical and optical properties. Amongthese methods, RC measurements can be more reliable, easier toimplement, and low cost. To perform a RC measurements, a physicalcontact should be maintained between the measuring electrodes of theapparatus or system and the tissue. The accuracy of these measurementscan be dependent on the contact force applied to maintain a physicalcontact between the measuring electrodes of the apparatus or system andthe tissue. If a RC measurement is performed using a rigid, planarelectrodes, contact force is applied to ensure that these electrodesremain in contact with the skin's curved, compliant surface. Forexample, existing hydration sensors with rigid, planar electrodes thatuse a RC measurement approach have built-in pressure sensing devices toaddress this issue. Additionally, existing hydration sensors with rigid,planar electrodes may be limited to instantaneous measurements due tothe lack of a reservoir for sweat storage. As a result, hydrationsensors with rigid, planar electrodes can be difficult to use and maynot provide continuous monitoring.

In a non-limiting example, the apparatus and systems described hereinprovide a new platform for collecting electrophysiological measurementsof tissue. The technology described herein enables the electronics to beintegrated on the tissue without requiring external mechanical loadingto maintain contact. Novel epidermal skin sweat sensor composed ofstretchable electrodes is described. Taking advantage of smallconductive structures feature size and a discrete open-mesh-typestructure, the apparatus described herein can be conformally applied onthe tissue surface. In an example implementation, to achieve continuousmonitoring capability, a cellulose pad can be mounted between theconductive structures and the tissue to serve as a sweat storage layer,and the entire structure is held together by an adhesive backing layer(such as but not limited to TEGADERM® (3M, St. Paul, Minn.). Thisbacking layer provides structural support and holds the apparatus intight contact with the tissue during measurements. With thisconfiguration, the skin sweat sensor apparatus described herein providesa viable solution for reliable and continuous sweat monitoring.

A system, apparatus and method described herein facilitates measurementof capacitance-based properties of the tissue. The capacitance-basedproperties of the tissue can be used to provide an indication of thetissue condition. As a non-limiting example, a system, apparatus andmethod described herein can facilitate measurement of the sweat rate ofthe tissue (which can be related to a level of hydration and/orde-hydration of the tissue). In this example, measurement ofcapacitance-based electrical properties can be used to provide anindication of the level of hydration and/or de-hydration of tissue.

FIG. 3 shows a cross-section view of an example apparatus 300 accordingto an example implementation that includes three conductive structures302-a, 302-b and 302-c disposed over a substrate 301. Substrate 301 canbe skin or any other tissue. The example apparatus 300 also includes alayer 306. Layer 306 can include an adhesive portion that adheres to aportion of the substrate 301 to assist in maintaining conductivestructures 302-a, 302-b and 302-c in contact with the substrate 301.

The illustration of FIG. 3 also shows an example electrical schematic ofan effective circuit representation of the electrical properties of thesubstrate when the three conductive structures 302-a, 302-b and 302-care disposed over the substrate 301. As illustrated in FIG. 3, when apotential (Vin) relative to ground (Gnd) is applied across neighboringpairs of conductive structures 302-a, 302-b and 302-c, effectivevariable capacitance terms develop proximate to the interface betweenthe conductive structures 302-a, 302-b and 302-c and the substrate 301,and effective variable capacitance and resistance term develop withinthe substrate 301. The effective circuit terms can be representelectrical properties of the apparatus and the tissue as follows:

R=ρl/A  (1)

where R is the electrical resistance, ρ is the resistivity, l is thelength in the tissue between the conductive structures, and AR is thecross-sectional area of current path through the tissue.

C=∈A/d  (2)

where C is the electrical capacitance, c is the permittivity, A is theoverlapping area between the conductive structures and the tissue, and dis the separation distance between the conductive structures. In anexample, the measurement of the electrical property of the substrate,such as but not limited to the tissue, among the three conductivestructures 302-a, 302-b and 302-c can be modeled based on the examplecircuit elements of FIG. 3 and using the expressions of equations (1)and (2).

An apparatus or system according to the principles herein for performingcapacitance-based measurements is not limited to solely three conductivestructures. For example, an example apparatus or system can include 2,5, 8, 10, 15 or more conductive structures (E1, E2 and E3, . . . , E(n),where n is an integer). For such a system, the effective circuit modelof FIG. 3 can be extended to any number of effective circuit elements,with effective capacitance terms (C1, C2, C3, . . . , C(j), where j isan integer), and effective resistance terms (R1, R2, . . . , R(k), wherek is an integer). FIG. 4 shows a cross-section view of another exampleapparatus 400 according to an example implementation that includes twoconductive structures 402-a, 402-b and 402-c disposed over a substrate401 (i.e., n=2). Substrate 401 can be skin or any other tissue. Theexample apparatus 400 also includes a layer 406. In an example, themeasurement of the electrical property of the substrate 301 or 401 amongthe neighboring conductive structures, or conductive structures in closeproximity, of the apparatus can be modeled based on the example circuitelements of FIG. 3 or FIG. 4, and extrapolated to model more components.The apparatus can be configured with any number n of conductivestructures. Increasing the number n of conductive structures may providefor increased accuracy of the measured capacitance across the systeminputs and outputs.

The conductive structures Ei (i=1, . . . 3) can include any applicableconductive material in the art, including a metal or metal alloy, adoped semiconductor, or a conductive oxide, or any combination thereof.Non-limiting examples of metals include Al or a transition metal(including Au, Ag, Cr, Cu, Fe, Ir, Mo, Nb, Pd, Pt, Rh, Ta, Ti, V, W orZn), or any combination thereof. Non-limiting examples of dopedsemiconductors include any conductive form of Si, Ge, or a Group III-IVsemiconductor (including GaAs, InP).

One or more of the conductive structures may be covered on at least oneside by a polymer-based material, such as but not limited to apolyimide. In an example, one or more of the conductive structures maybe encased in the polymer-based material. The polymer-based material canserve as an encapsulant layer.

Layer 306 or 406 may be a protective, encapsulating and/or backing layermade of a stretchable and/or flexible material. Non-limiting examples ofmaterials that can be used for layer 306 or 406 include any applicablepolymer-based materials, such as but not limited to a polyimide or atransparent medical dressing, e.g., TEGADERM® (3M, St. Paul, Minn.).

In a non-limiting example, layer 306 or 406 may be an encapsulationlayer that is disposed over at least a portion of the at least twoconductive structures. In an example, the encapsulation layer can be apolymer. In another example, portions of the encapsulation layer caninclude an adhesive, and wherein the adhesive maintains the portions ofthe encapsulation layer in physical contact with the tissue (includingattaching it to the tissue). In this manner, the apparatus can bemaintained in contact with the tissue.

In another example, an electrically conductive gel can be disposedbetween the apparatus and any absorbing layer present between theapparatus and the tissue. The conductive gel can deform easily and allowthe spacing to change, but maintain the electrical distance between theapparatus and the absorber at substantially zero.

Substrate 301 or 401 may be a portion of tissue, such as but not limitedto the skin, a muscle tissue, heart tissue, etc.

FIG. 5 shows an example apparatus 500 that includes ten (10)interdigitated conductive structures 502. The example apparatus 500 canbe disposed over the tissue to perform the electrical measurementsaccording to the principles described herein. The capacitance-basedmeasurement can be performed by applying a potential across theinterdigitated conductive structures. In the example of FIG. 5, theinterdigitated conductive structures 502 are disposed substantiallyparallel to each other. Each of the interdigitated conductive structures502 has a non-linear configuration. In the example of FIG. 5, theconductive structures 502 have a serpentine configuration. In otherexamples, non-linear configuration of the conductive structures 502 canbe a, a zig-zag configuration, a rippled configuration, or any othernon-linear configuration. The non-linear configuration of the conductivestructures can facilitate greater sampling of the electrical propertiesof the tissue and higher signal to noise than linear electrodes. Thenon-linear configuration of the conductive structures also facilitatesmore consistent performance of the apparatus with deformation such asstretching. The example apparatus 500 also includes two brace structures504, each disposed substantially perpendicularly to the overallorientation of the interdigitated conductive structures 502, and atleast one spacer structure 506 that is physically coupled at each of itsends to a portion of each of the at least two brace structures. Each ofthe brace structures 504 is in electrical communication with alternatingones of the conductive structures 502. For example, conductivestructures 502-e are in electrical communication with one of the bracestructure 504 while the alternating, interposed conductive structure502-f is not in electrical communication with that brace structure 504.The spacer structure 506 facilitates maintaining a substantially uniformseparation between the brace structures 504. The spacer structure 506can also facilitates maintaining a substantially uniform form factorduring deformation of the apparatus. A measure of the electricalproperty of tissue using the example apparatus 500 can be used toprovide an indication of the condition of the tissue according to any ofthe principles described herein.

The example apparatus 500 may also include contacts 508 that providesfor electrical communication between the apparatus 500 and at least oneother component, as described hereinabove and in connection with FIG. 1Aor 1B. For example, the at least one other component can be a batterythat applies a potential across the contacts 508, and in turn acrossneighboring conductive structures 502. in an example, a system isprovided according to the principles described herein that includesapparatus 500 and at least one other component (as described hereinabove).

The conductive structures and the brace structures can include anyapplicable conductive material in the art, including a metal or metalalloy, a doped semiconductor, or a conductive oxide, or any combinationthereof. Non-limiting examples of metals include Al or a transitionmetal (including Au, Ag, Cr, Cu, Fe, Ir, Mo, Nb, Pd, Pt, Rh, Ta, Ti, V,W or Zn), or any combination thereof. Non-limiting examples of dopedsemiconductors include any conductive form of Si, Ge, or a Group III-IVsemiconductor (including GaAs, InP). In an example, the conductivestructures and the brace structures can be formed from the sameconductive material. In another example, the conductive structures andthe brace structures can be formed from different conductive materials.

The conductive structures and/or the brace structures may be covered onat least one side by a polymer-based material, such as but not limitedto a polyimide. In an example, the conductive structures and/or thebrace structures may be encased in the polymer-based material. Thepolymer-based material can serve as an encapsulant layer.

Spacer structure also may be formed from a polymer-based material.

Apparatus 500 or a system that includes apparatus 500 may include aprotective and/or backing layer made of a stretchable and/or flexiblematerial. Non-limiting examples of materials that can be used for theprotective and/or backing layer include any applicable polymer-basedmaterials, such as but not limited to a polyimide or a transparentmedical dressing, e.g., TEGADERM® (3M, St. Paul, Minn.). The protectiveand/or backing layer can include an adhesive portion that adheres to aportion of the substrate to assist in maintaining the conductivestructures 502 in contact with the substrate (including the tissue).

In a non-limiting example, the dimensions and morphology of the sensingcomponent can be maintained using the spacer structure 506. In anexample, the spacer structure 506 is formed from an insulating materialor another material with lower conductivity than the conductivestructures or the brace structures. The properties of the spacerstructure 506 of the apparatus 500 can facilitate little or no currentdirectly passing from one brace structure to the other brace structureby way of the spacer structure 506. Rather, current passes from one setof the conductive structures 502 to another set of the conductivestructures 502 by way of the underlying tissue.

In an example according to FIG. 5, the length of the ripples of thebrace structure may be uniform or may vary from one side of theapparatus 500 relative to the other.

In a non-limiting example, the non-linear configuration of theconductive structures facilitates increased flexibility of theapparatus. For example, the non-linear geometry can facilitate increasedflexibility of the apparatus to stretching, torsion or other deformationof the underlying tissue, and the apparatus maintains substantialcontact with the tissue in spite of the stretching, torsion or otherdeformation.

FIG. 6 is an illustration of the example apparatus 500 of FIG. 5, withselected portions magnified. FIG. 6 shows a magnification of a portionof the apparatus 500 where a side of the brace structure 504 (lightercolored segment) forms an interface 510 with the spacer structure 506.FIG. 6 shows a magnification of an interface 512 between a bracestructure 504 and a conductive structure 502, which also shows thatalternating ones of the interdigitated conductive structure 502 makesphysical contact with the brace structure 504.

FIG. 7 shows a non-limiting examples of the apparatus 500 includingcross-link structures 515 that can be formed according to the principlesherein. The cross-link structures 515 can provide increased mechanicalstability of the structure during fabrication (e.g., during a transferprocess from a substrate and/or a printing and extraction process toanother substrate), and in use, e.g., to stabilize the sensor againststretching, flexing, torsion or other deformation of the substrate it isdisposed on. For example, the cross-link structures 515 can aid inmaintaining a form factor, including ratios of dimensions, during and/orafter a stretching, elongation or relaxing of the apparatus. Forexample, the cross-link structures 515 can be formed across any pair ofthe conductive structures 502 of FIG. 5, at any position along theirlength. In the examples shown, the cross-links structures 515 are formedin a serpentine (“S”) shape. In other examples, the cross-linkstructures 515 can be formed as substantially straight crossbars, formedin a zig-zag pattern, formed as arcs, or ripples, or any othermorphology that facilitates maintaining a mechanical stability and/or aform factor of the apparatus. In addition, the cross-link structures 515can be formed as at least two cross-link structures that are formedacross neighboring electrodes. The cross-link structures 515 can beformed from a polymer-based material or any other stretchable and/orflexible material. In addition, while the positioning of the examplecross-link structures 515 are shown to be roughly aligned in thex-direction of the FIG. 7, cross-link structures 515 also can bedisplaced relative to each other in the x-direction.

In the example of FIG. 7, the cross-link structures 515 can be formed ofsubstantially the same encapsulant material that covers portions of theinterdigitated conductive structures, and extend seamlessly from them.In this example, these cross-link structures 515 can be formed duringthe same process step that disposes the encapsulant polymer-basedmaterial on portions of the interdigitated conductive structures. Inanother examples, the cross-link structures 515 can be formed of adifferent material from the encapsulant material that covers portions ofthe interdigitated conductive structures.

FIGS. 8 through 10 illustrate another example implementation of anapparatus that is configured to measure electrical properties of thetissue through a capacitance-based measurement. As shown in FIG. 8, theapparatus 800 can include at least two conductive structures 802 thatrun substantially parallel to each other along substantially an entirelength of the conductive structures 802. Each of the conductivestructures 802 can have a curved configuration. Apparatus 800 accordingto this example implementation also can include at least two contactstructures 804. Each of the at least two contact structures 804 is inelectrical communication with at least one of the at least two parallelconductive structures 802. The capacitive-based measurement can beperformed by applying a potential across the at least two conductivestructures 802 using the at least two contact structures 804. A measureof the electrical property of the tissue using the apparatus 800 is usedto provide an indication of the condition of the tissue according to anyof the principles described herein.

While the examples of FIG. 8 through 10 are illustrated with two curvedconductive structures 802, other examples according to the principlesherein can include three, four or more curved conductive structures 802that are disposed substantially concentrically and are in electricalcommunication with contacts 804.

The conductive structures 802 and the contact structures 804 can includeany applicable conductive material in the art, including a metal ormetal alloy, a doped semiconductor, or a conductive oxide, or anycombination thereof. Non-limiting examples of metals include Al or atransition metal (including Au, Ag, Cr, Cu, Fe, Ir, Mo, Nb, Pd, Pt, Rh,Ta, Ti, V, W or Zn), or any combination thereof. Non-limiting examplesof doped semiconductors include any conductive form of Si, Ge, or aGroup III-IV semiconductor (including GaAs, InP). In an example, theconductive structures 802 and the contact structures 804 can be formedfrom the same conductive material. In another example, the conductivestructures 802 and the contact structures 804 can be formed fromdifferent conductive materials.

The conductive structures 802 and/or the contact structures 804 may becovered on at least one side by a polymer-based material, such as butnot limited to a polyimide. In an example, the conductive structures 802and/or the contact structures 804 may be encased in the polymer-basedmaterial. The polymer-based material can serve as an encapsulant layer.

Apparatus 800 or a system that includes apparatus 800 may include aprotective and/or backing layer made of a stretchable and/or flexiblematerial. Non-limiting examples of materials that can be used for theprotective and/or backing layer include any applicable polymer-basedmaterials, such as but not limited to a polyimide or a transparentmedical dressing, e.g., TEGADERM® (3M, St. Paul, Minn.). The protectiveand/or backing layer can include an adhesive portion that adheres to aportion of the substrate to assist in maintaining the conductivestructures 802 in contact with the substrate (including the tissue).

As shown in FIG. 9, the apparatus may include cross-link structures 815.The cross-link structures 815 can provide increased mechanical stabilityof the structure during fabrication (e.g., during a transfer processfrom a substrate and/or a printing and extraction process to anothersubstrate), and in use, e.g., to stabilize the sensor againststretching, flexing, torsion or other deformation of the substrate it isdisposed on. For example, the cross-link structures 815 can aid inmaintaining a form factor, including ratios of dimensions, during and/orafter a stretching, elongation or relaxing of the apparatus. Forexample, the cross-link structures 815 can be formed across any pair ofthe conductive structures 802 of FIG. 5, at any position along theirlength. In the examples shown, the cross-links structures 815 are formedin a serpentine (“S”) shape. In other examples, the cross-linkstructures 815 can be formed as substantially straight crossbars, formedin a zig-zag pattern, formed as arcs, or ripples, or any othermorphology that facilitates maintaining a mechanical stability and/or aform factor of the apparatus. In addition, the cross-link structures 815can be formed as at least two cross-link structures that are formedacross neighboring electrodes. The cross-link structures 815 can beformed from a polymer-based material or any other stretchable and/orflexible material.

In the example of FIG. 9, the cross-link structures 815 can be formed ofsubstantially the same encapsulant material that covers portions of theconductive structures, and extend seamlessly from them. In this example,these cross-link structures 815 can be formed during the same processstep that disposes the encapsulant polymer-based material on portions ofthe conductive structures. In another examples, the cross-linkstructures 815 can be formed of a different material from theencapsulant material that covers portions of the conductive structures815.

FIG. 10 shows magnifications 810 and 812 of the interface between theconductive structures 802 and leads 807. Leads 807 provide forelectrical communication between conductive structures 802 and contacts804. As shown in the magnifications 810 and 812 of FIG. 10, one of theconductive structures 802 is separated from lead 807 by a spacerstructure 806. In an example, the spacer structure 806 is formed from aninsulating material or another material with lower conductivity than theconductive structures 802 or the leads 807. The properties of the spacerstructure 806 of the apparatus 800 can facilitate little or no currentdirectly passing from one conductive structure 802 to the lead 807 byway of the spacer structure 806. Rather, current passes from one set ofthe conductive structures 802 to another set of the conductivestructures 802 by way of the underlying tissue. Spacer structures 806also may be formed from a polymer-based material.

A non-limiting example process for fabricating the example apparatus ofany of FIGS. 5 through 10 is illustrated in FIGS. 11A-11I. In FIG. 11A,a fabrication substrate 1100, such as but not limited to a siliconsubstrate or a substrate for group III-V electronics, is coated with awith a sacrificial release layer 1102. In a non-limiting example, thesacrificial release layer 1102 is a polymer such aspolymethylmethacrylate (PMMA). In FIG. 11B, the sacrificial releaselayer 1102 is patterned. In FIG. 11C, a first polymer layer 1104 is spincoated onto the sacrificial release layer 1102. In an example, the firstpolymer layer 1104 can be a polyimide. In FIG. 11D, a layer ofconductive material 1106 is deposited over the first polymer layer 1104to form the conductive structures. In FIG. 11E, where applicable to theconductive material 1106 used, a lithography process may be performed topattern the conductive material 1106 into any of the configurations ofconductive structures described herein. In FIG. 11F, a second polymerlayer 1108 is spin coated over the conductive structures. In an example,the second polymer layer 1108 can be a polyimide. In FIG. 11G, thesecond polymer layer 1108 is patterned. In FIG. 11H, the sacrificialrelease layer material is selectively removed. For example, where thesacrificial release layer material is PMMA, acetone can be used forselective removal. At this stage, the apparatus 1110 is in substantiallyfinal form and attached to the fabrication substrate. In FIG. 11I, atransfer substrate 1112 is used to remove the apparatus 1110 from thefabrication substrate 1100.

FIGS. 12A through 12E show an example implementation of an exampleapparatus that includes the interdigitated conductive structures. FIG.12A shows that the example apparatus can be fabricated in dimensionscomparable to a coin. The dimensions of the electrodes are 100 μm wide,and 0.5 μm thick. Due to the open-mesh electrode structure, the strainon the conductive structures due to tissue stretching can be limited.The turning angle [7] on the conductive structures is designed as −25degree. In addition, the stretchable conductors interconnecting theconductive structures play a role during stretching. In this regard, theturning angle of the stretchable conductors is designed as 0 degree. Inthis example, both the electrodes and the stretchable conductors aremade of gold (Au) and are fully encapsulated in polyimide (PI) formechanical reliability. The polyimide is 10 μm thick on both top andbottom of the electrodes. FIG. 12B shows the example apparatus disposedon skin using a protective layer before a measurement is made. FIG. 12Cshows the example apparatus under a length-wise stretching deformation.FIG. 12D shows the example apparatus under a diagonal stretchingdeformation. In each of these scenarios, the example apparatus isconfigured such that it returns to substantially its original formfactor once the deformation force is removed. FIG. 12E shows the exampleapparatus being removed from the skin.

An example implementation of a measurement using an example apparatus orsystem described herein is as follows. The effective circuit terms modelof an example apparatus or system described herein (such as but notlimited to the effective circuits illustrated in FIGS. 3 and 4) can beused to model electrical measurements performed using the apparatus ofFIGS. 5 through 7 or the apparatus of FIGS. 8 through 10. For example,the effective circuit described in connection with FIG. 3 can be used tomodel a measurement across a line through portion “A” of FIG. 5, orextrapolated to model the plurality of conductive structures of theentire interdigitated structure. As another example, the effectivecircuit described in connection with FIG. 4 can be used to model ameasurement across a line through portion “B” of FIG. 8.

The analyzed electrical measurements made using an apparatus accordingto the principles described herein in connection with any of FIGS. 5through 10 can be used to provide an indication of changes in the tissuecondition. For example, the effective circuit terms near the interfacein FIG. 3 or FIG. 4 are observed to be sensitive to changes in tissuecondition, such as but not limited to the sweat rate of the underlyingtissue (which can be related to its hydration level). Within thesubstrate, the variable capacitance and resistance terms develop betweenthe conductive structures. These effective terms are observed to besensitive to the sweat level of the tissue (which can be related tohydration levels) and//or stretching of the example apparatus or systemand/or the underlying tissue.

An example method is provided herein for determining tissue conditionbased on the measurement of the electrical property of the substrateusing a capacitance-based measurement. The method includes receivingdata in connection with a measurement of the electrical properties ofthe tissue, and applying a model to the data to quantify at least oneparameter of the effective circuit model. The value of the parameter canbe used to provide an indication of the tissue condition.

In an example system, apparatus and method, any of the apparatusdescribed hereinabove can be disposed on to perform the measurement ofthe electrical properties. In an example, the sensor is configured towithstand deformation in more than one direction (for example, in x, yand/or z-direction). In a non-limiting example system, apparatus andmethod herein, a fully conformal sensor that includes an apparatusdescribed herein is provided. The fully conformal sensor can be placedon, including being attached on. a variety of surface profiles, withminimal to no effect on the functionality of the sensor to detect tissueconditions, such as but not limited to a sweat level (which can berelated to a hydration level), a tissue disease state, or mechanicalproperties of the tissue.

As a non-limiting example, the value of the parameter can be comparedand/or correlated to a calibration standard of tissue condition versusthe value of the circuit parameter. The calibration standard can begenerated based on a training set of electrical measurements of tissue,or material similar to tissue, that exhibits the condition that issought to be characterized. For example, the training set can includetissue at various stages of a disease condition, where the correlationbetween the electrical measurements and the known disease stage can beused to generate the calibration standard applied to tissue of unknowndisease state. As another example, the training set can include tissueat various hydration levels. The correlation between the electricalmeasurements and the known hydration levels can be used to generate thecalibration standard applied to tissue of unknown hydration level.

The configurations of the apparatus described herein, including thediscrete interdigitated structure, allow the apparatus deformation toaccommodate the natural motions of the tissue. The mechanics of theapparatus, particularly the stretching deformation, can affect apparatusperformance. The stretching deformation can change the electricalproperties of the system since the distance between the conductivestructures is one of the parameters in the RC measurement. FIG. 13Ashows a finite element (FE) model for deformation mechanism simulationand FIG. 13B shows a hydration sensor stretched at 50% elongation. Themetal is Au and can be modeled as a plastic deformable solid obeying thebi-linear kinematic hardening rule. The Young's modulus is set at 30 e³MPa, yielding stress is 204 MPa, and the tangent modulus is 4769 MPa.The polyimide of the cross-link structures and the conductive structurescoating is modeled as linear elastic with a Young's modulus of 3.2 e³MPa, and the backing layer (TEGADERM®) is modeled as a three-factorhyper-elastic Mooney-Rivlin solid. The three factors of thehyper-elastic Mooney-Rivlin model are: C₁₀=−0.13, C₀₁=0.57, andC₁₁=0.13. The FE model corresponds to the stretching test, as shown inFIG. 13B.

FIG. 14A shows an example apparatus that includes interdigitatedconductive structures in its relaxed state. FIG. 14B shows the exampleapparatus of FIG. 14A subjected to about 50% elongation. Non-limitingexamples of the measurement of the electrical properties of a substrateusing an example apparatus such as shown in FIGS. 14A and 14B aredescribed with reference to FIGS. 15A through 16B. The measurement canbe used to quantify a complex ratio of the voltage to the current in acircuit through portions of the tissue as described above. Theelectrical properties can be quantified based on a magnitude and/or aphase of the electrical properties.

In a non-limiting example, the apparatus of FIG. 14A is used to measurethe hydration level of the patch, which can be related to the sweat rateof an individual. In this example, the substrate is a cellulose pad.FIG. 15A shows the magnitude and FIG. 15B shows the phase of theimpedance change with the sweat level range from 20 to 80 percentsaturation at selected measurement frequencies (the radio frequency (RF)range from 20 to 80 kHz). In this example implementation, the sweatlevel is defined as the ratio of the volume of saline to the volume ofthe substrate, normalized such that 100 corresponds to full-saturation.The volume of saline added is varied, and the volume of the cellulosepad is held constant (450 mm³). Initial measurements over a range offrequencies are performed to determine which frequency has the maximumchange of impedance across the hydration levels, thus providing optimalsensitivity. FIG. 15A shows that the magnitude of the impedance at 20kHz drops by 0.38 MΩ, while the impedance phase shifts by −2.13 degreesas the sweat level changes from 20 to 80 percent saturation. That is, 20kHz provides the most sensitive output of impedance magnitude in this RFrange. As the sweat level increases, the impedance drops at the RF rangefrom 20 kHz to 80 kHz. This behavior can be attributed to an increase inelectrical conductivity: increasing the amount of saline in thecellulose pad provides more ionic pathway for charge transport.

When mounted on a sweat-absorbing patch, the response of the exampleapparatus to fluid in the patch is quantifiable. The volume of analyterequired to saturate the patch is determined in advance, then analyte istitrated onto a dry patch to systematically increase the hydrationlevel. A dramatic drop in impedance is found between 0 and 20%hydration, after which the decline is more gradual.

The electrical performance of the example apparatus and system isobserved to change as they are subjected to deformation. The change inelectrical performance with changes in the tissue condition, includingthe changes of “resistive” impedance (R) and capacitance (C), can bedescribed relative to equation (1) and (2).

The changes in electrical property of the substrate with changes intissue condition can be described based on a change in the hydrationstate of the tissue as follows. As the sweat level in the substrateincreases, the resistivity (ρ) decreases whereas the permittivity (∈)increases, resulting in the impedance (based on the resistance) droppingand capacitance rising. The decrease in resistivity can be due to theincrease of mobile ions within the substrate. On the other hand, theincreasing of permittivity can be explained by increasing the dipolesprimarily detected by volume of sweat in the cellulose pad. These twofactors (ρ and ∈) are primarily dominated by the sweat level in thecellulose pad. It should be noted that the sensor performance is alsosensitive to structural parameters such as the distance between theconductive structures. According to eq. (1) and (2), as the length (land d) between conductive structures increases because of stretching,the electrical resistance increases whereas the capacitance decreases.

As described herein, an example apparatus can be mechanically designedfor comfortable wear on tissue by employing nonlinear conductivestructures in a stretchable structure. The example apparatus can beconfigured to be sensitive to measuring frequency, sweat level andstretching deformation.

In an example implementation described in connection with FIGS. 16A and16B, a 20 kHz signals is observed to provide sensitive performance:electrical impedance changes 50% while sweat level increases from 20 to80 percent saturation. In addition, sensor elongation from 15 up to 50%affected the measurement sensitivity of both electrical impedance andcapacitance. FIGS. 16A and 16B show performance of the example apparatusversus impedance and capacitance, respectively, while the exampleapparatus is being subjected to stretching at various sweat levels.

Specifically, FIGS. 16A and 16B show the impedance and capacitancechange, respectively, of the example apparatus while stretched and atsweat level ranging from 20 to 80 percent saturation. The measurementsare conducted at 50 kHz. As shown in FIG. 16A, the impedance increasesnonlinearly with stretching due to the increasing length (l) betweenelectrodes. In addition, the apparatus appears to lose sensitivity withrespect to the sweat level when elongations become very large. FIG. 16Bshows a similar trend for capacitance: the performance of the apparatusdecreases nonlinearly about 80% when stretching for 15% elongation. Theperformance of the apparatus appears to degenerate substantially when itis stretched beyond 40% and neither impedance nor capacitance can bemeasured respective to the sweat level. The performance reduction may bedue to the out-of-plane deformation on the stretchable interconnectscausing conductive structures to lose contact with the substrate. Also,the resistive impedance and capacitance are not linear relationship tothe structural parameters, l and d, as described in connection withequations (1) and (2). During stretching, however, there is a morecomplex deformation mechanism that causes the nonlinear relationship tothe output of the electrical performance.

FIG. 17 shows a simulation of the distance changes (d) between theconductive structures during stretching of the substrate. The distancechange between the conductive structures and the elongation are notone-to-one proportional factors. At 15% elongation, the distance changes9% between electrodes. However, at the same elongation, the electricalperformance of the sensor drops 80%. This performance drop may be due toout-of-plane deformation on the stretchable interconnects duringstretching. FIG. 18 shows the simulated out-of-plane deformation whilethe inset to FIG. 18 shows the optical image of the stretchableinterconnect. The color difference of the stretchable interconnect inthe inset image is due to the out-of-plane deformation causes the lightto reflect differently. At 15% elongation, the stretchable interconnectdeforms by 0.14 mm in a Z-direction. This out-of-plane deformation canincrease both the separation distance (d) and the length of theresistive impedance (l). As a result, not only the distance betweenelectrodes but also the out-of-plane deformation affects the electricalperformance.

An example method is provided herein for determining tissue conditionbased on the measurement of the electrical property of the substrateusing a capacitance-based measurement at performed at an optimalfrequency. The method includes receiving data in connection with ameasurement of the electrical properties of the tissue, where themeasurement is performed at a frequency that provides the most sensitiveoutput of impedance magnitude in the RF range, and applying a model tothe data to quantify at least one parameter of the effective circuitmodel. In an example, the frequency is about 20 kHz. The value of theparameter can be used to provide an indication of the tissue conditionand/or to quantify the amount of stretching of the example apparatus.

Another example method provided herein for determining tissue conditionbased on the measurement of the electrical property of the substrateusing a capacitance-based measurement that allows for a certain degreeof deformation of the example apparatus. The method includes receivingdata in connection with a measurement of the electrical properties ofthe tissue, where the example apparatus used to make the measurement issubjected to a degree of deformation during the measurement, andapplying a model to the data to quantify at least one parameter of theeffective circuit model. The value of the parameter can be used toprovide an indication of the tissue condition.

With respect to other hydration monitoring techniques, sweat analysis,blood analysis, muscular ultrasound analysis, and electrical analysisalso can be performed. These other hydration monitoring techniques canbe used to provide potential ways of corroboration or calibrating ahydration monitoring measurement performed according to a principleherein. Sweat analysis (via ionic concentration analysis) and bloodanalysis (via hemoglobin concentration) both may present practicalissues in non-invasive sample collection as well as the scalability ofthe necessary components.

Using capacitance sensing to monitor hydration can present severalbenefits as compared to blood and sweat analysis:

-   -   Blood and sweat analysis may likely require disposable, adhesive        sensor units and may be costly.    -   There are specific locations, including the thigh and upper        bicep, at which capacitance sensing works better for hydration        monitoring, and these locations are conducive to use of a device        during vigorous activity. The best locations for a sweat or        blood monitoring system might be harder to determine.    -   The capacitance sensing can be completely non-invasive.

Such sensors have been worn for periods of up to a week withoutdiscomfort, and survive daily activities such as exercise and showering.Lifetime is primarily limited by the turnover of cells in the skin.

A system, apparatus and method according to a principle herein providesthe following benefits:

-   -   The sensor circuitry can be configured to be fully flexible,        stretchable and conformable for a more comfortable and portable        user experience, whether incorporated into an arm/leg band or a        form-fitted garment.    -   Hydration status may be viewed in real-time based on        measurements using a sensor incorporated in an article of        clothing or gear, including an arm/leg band or form-fitted        clothing item, or a patch placed on the skin.    -   An example device may include a sensor coupled to LED indicator        lights for indicating sweat level (which can be related to        hydration level).    -   An example device may include a sensor described herein in a        patch placed on the skin, or an article of clothing or gear,        that is configured to transmit data (including by wireless        communication or using IR); a handheld device (such as but not        limited to a smartphone), can be brought in proximity to the        sensor to receive a quantitative indication of the electrical        measurement performed by the sensor    -   The arm/leg band may be wireless and transmit data to mobile        devices and portable music players.    -   Through innovative low-power management techniques the circuit        can operate on a very small power source.    -   Through innovative electronic circuit design, small changes in        capacitance (and in some examples impedance measurements as        well) can be detected.

A sensor for performing capacitance measurements may be fabricated on aflexible and/or stretchy substrate that may be worn on the skin,including as a skin patch, or integrated into form-fitted clothing orother gear (such as an arm or leg band). In one example, the sensor isdesigned with a serpentine geometry to allow the sensor to flex with theflexible and/or stretchy substrate. The sweat level (which can berelated to a state of hydration) is determined by measuring thecapacitance between the two contacts of the capacitance sensor. Changesin a measured capacitance can reflect changes in the state of hydration.

It is also contemplated that this sensor may be used in combination withother types of sensors that measure the composition of sweat (e.g.,sensors that measure conductivity or sensors that measure theconcentration of selective ions such as sodium potassium and calcium,and others).

A system, method and apparatus according to a principle described hereincan be relevant to at least four commercial segments. The first segmentis athletics—including both casual and highly competitive athletics.Hydration level measurement can help athletes greatly in monitoringtheir training routine as well as offer a safety precaution to helpprevent excessive dehydration. The systems, apparatus and methodsdisclosed here are used to indicate when an athlete needs to drink morewater or electrolyte solutions like a sport or energy drink. The secondapplicable segment is the military. Soldiers, pilots, etc. may benefitgreatly from hydration monitoring during live combat and training.Dehydration, even at small levels, can impact physical and mentalperformance and pose serious safety issues. Monitoring hydration levelscan help a soldier remain hydrated to avoid any of these risk factors.The third potential market segment is the beauty and cosmetics marketwhere local skin hydration may be monitored and various lotions or otherproduct applied when the state of hydration is deemed too low.Appropriate levels of hydration can prevent skin from drying out and,over time, create healthy skin appearance. In another example, the levelof hydration can serve as an indicator of skin firmness. The fourthsegment is in the health and wellness/medical monitoring market. Thismay be part of a general wellness program where hydration levels aremonitored as one of many health measurements and be integrated intogeneral assessment for health tracking, diagnosis and long-termmonitoring.

Inductance-Based Measurements

In an example according to the principles described herein, an apparatuscan be configured to measure electrical properties of the tissue throughan inductance-based measurement.

A non-limiting example of an apparatus 1900 for performinginductance-based measurement is shown in FIG. 19A. An apparatus 1900according to this example implementation can include a substrate 1902disposed above the tissue, where the substrate 1902 is formed from amaterial that exhibits a change in a state with a change in tissuecondition. As a non-limiting example, the substrate 1902 can be formedfrom a material that changes hydration state with a change in the sweatlevel of the tissue (which can be related to hydration level). Theapparatus 1900 further includes at least one first inductor structure1904 disposed above the substrate. As non-limiting examples, theinductor structure 1904 can be a spiral coil structure, a cylindricalcoil structure, or a toroidal structure. The inductance-basedmeasurement can be performed by applying a potential to the at least onefirst inductor structure 1904. An electrical property and/or a physicalproperty of the at least one first inductor structure 1904 changes withthe change in the state of the substrate. A measure of the electricalproperty or the physical property of the at least one first inductorstructure 1904 using the apparatus is used to provide an indication ofthe tissue condition. The apparatus 1900 further includes anencapsulation layer 1906.

In an example, the electrical property can be a magnetic flux densityfrom the at least one first inductor structure.

In an example, the encapsulation layer 1906 can be a polymer, includinga polymer having an adhesive portion. For example, the adhesive portionof the encapsulation layer 1908 can be present where the encapsulationlayer 1906 makes physical contact with the tissue (including attachingthe apparatus to the tissue). The adhesive portions can be used to mountthe apparatus 1900 to the tissue. In this manner, the apparatus can bemaintained in contact with the tissue.

In another example, an electrically conductive gel can be disposedbetween the apparatus and any absorbing layer present between theapparatus and the tissue. The conductive gel can deform easily and allowthe spacing to change, but maintain the electrical distance between theapparatus and the absorber at substantially zero.

In an example, the electrical property is a magnetic flux density fromthe at least one first inductor structure that reaches the region.

As shown in FIG. 19B, an apparatus 1900 for performing inductance-basedmeasurement can include the substrate 1902, at least one first inductorstructure 1904 and an encapsulation layer 1906. The apparatus furtherincludes a separator layer 1908 disposed between the at least one firstinductor structure 1904 and the substrate 1902.

In an example, the separator layer is a non-conductive material,including a material based on a polymer.

In an example implementation, a reader can be used to perform theelectrical measurement of the tissue. As shown in FIG. 20, an examplereader 1910 can include at least one second inductor structure 1912. Ameasure of a change in an electrical property of the at least one secondinductor structure 19192 brought in proximity to the at least one firstinductor structure 1904 provides the measure of the electrical propertyof the at least one first inductor structure 1904. The measure of theelectrical property or the physical property of the at least one firstinductor structure 1904 using the reader 1901 is used to provide anindication of the tissue condition. For example, a calibration standardcan be generated as described above (in connection with thecapacitance-based system) based on inductance-based electricalmeasurements of a training set of tissue samples in different knowntissue conditions.

The second inductor structure 1912 can be the same configuration as thefirst inductor structure 1904.

In a non-limiting example, the reader is a handheld device such as asmartphone, a tablet, a slate, or other handheld computing device. Aprocessor of the handheld device can be used to analyze the data fromthe inductance-based measurement to provide the indication of the tissuecondition.

RF inductor coils are used that are sensitive to the impedance of theunderlying tissue. Likewise, a passive RF induction coil on the skin tomeasure changes in impedance of the underlying tissue may be correlatedwith changes in the state of hydration of the tissue. This offers asimple and non invasive method for hydration assessment that can easilybe integrated into a wearable (stretchy, flexible or conformal) formfactor.

Using tissue impedance-inductance to monitor hydration has the severalspecific advantages over blood and sweat analysis: Blood and sweatanalysis can require disposable, adhesive sensor units and may becostly. A RF inductor can easily be designed to be reusable. There arespecific locations, including the thigh and upper bicep, at which RFimpedance testing works best for hydration monitoring, and theselocations are conducive to use of a device during vigorous activity.

An RF inductor coil may be fabricated on a flexible and/or stretchysubstrate that may be worn on the skin or integrated into form-fittedclothing. The tissue condition, including its state of hydration, isdetermined by measuring the resonant frequency of the coil. Thisfrequency is related to the impedance of the tissue adjacent to thecoil. Changes in resonant frequency may be correlated with changes inimpedance, which in turn reflects changes in the state of hydration. Thedepth of tissue to which the coil is sensitive to changes in impedancescales with the radius of the coil. Small coils (<1 cm) are designed tobe sensitive primarily to the hydration of the skin while larger coils(>1 cm) are designed to be sensitive to the state of hydration ofmuscle.

In accordance with various examples herein, the apparatus can be used toprovide real-time data giving information such as:

-   -   1. Total volume of sweat lost;    -   2. Composition of the sweat lost (major electrolytes lost in        sweat are Sodium, Potassium, Calcium) with an active monitor.

Example apparatus and systems herein for real-time monitoring ofhydration through a passive, non-invasive device based on volume ofsweat lost through the placement of RF conductor coils on a hydrophilicpatch (i.e. hydrophilic polyurethane) over a constant surface area ofthe skin. The RF coil and the patch may be housed in a bioadhesive patchthat contacts the skin and only allows for sweat from the specificsurface area to be collected. The hydrophilic patch—such as TECOPHILIC®(Lubrizol Corporation, Wickliffe, Ohio)—collects the amount of sweatlost over that surface area and distributes it uniformly. The changes inresonant frequency of the RF coil on top of the hydrophilic patch can becorrelated to the changes of impedance in the hydrophilic patch as thesweat accumulates. The changes can be measured through the use of aportable (handheld) RF reader. A small RF coil can be used to measurethe uniform distribution of the sweat accumulated in the hydrophilicpolyurethane patch over the surface area noted above. The correlateddata can then give a state of hydration based on volume of sweat lostover the entire Body Surface Area (BSA) by extrapolating the surfacearea of the patch over the surface area of the entire body. The averageBSA is widely taken to be 1.73 m² for an adult with 1.9 m² for a maleand 1.6 m² for a female. This can be further customized if both heightand weight are known through the Dubois & Dubois formula for BSA (oranother formula for BSA that is agreed upon):

${{BSA}( m^{2} )} = {{0.007184 \times {{weight}({kg})}^{0.416} \times {{height}({cm})}^{0.729}} = \frac{{{weight}({kg})}^{0.429} \times {{height}({cm})}^{0.729}}{139.2}}$

The example apparatus can be housed in an elastomeric patch adhering tothe skin. The patch may include a cavity containing an absorbent wickinghydrophilic material that draws and distributes sweat lost duringexertion. The patch may be designed in such away that the accumulationof sweat in the hydrophilic materials correlates directly with flux ofsweat through the skin: that is, amount of sweat per square-meter ofskin. This flux multiplied by the BSA calculated above gives ansubstantially absolute measure of the amount of fluids lost over aperiod of time. The wearer can then replenish or rehydrate withprecisely the amount of fluids lost. The patch may include an elastomerhaving pores restricting access to the skin and allowing a controlledflow of sweat into the cavity. An RF coil on the outer surface of thepatch may be stimulated by an external swept-frequency RF transceiver.The center frequency and Q of the coil changes in response to themoisture content of the patch, which will be detected by the externaltransceiver. The baseline for this measurement is the patch when it isfirst applied to skin.

Another implementation includes a metal mesh on the lower surface of theelastomer, either on the skin side or the bottom of the cavity. The meshisolates the skin surface from the RF sensing coil and substantiallyeliminates the natural variation of coil response depending onindividual body composition and starting hydration, allowing one-timefactory calibration of the patches.

Another example implementation includes an embedded sensing coil insidethe cavity and providing isolation both above and below the cavity. Theisolation helps protect the sense coil from subject variations as wellas stray electromagnetic fields. A separate communications coil linkedto the sense coil but outside the shielded cavity may be included inthis instantiation. The link may be either passive or active. A passivelink may be AC coupled or DC coupled. An active link may containtransistors, RF energy harvesting and storage, Rx, sense, and Tx phases,timing and control, similar to an RFID tag.

The example apparatus of FIG. 21 shows a quarter of a sensing patch 2100that includes an elastomer substrate 2102, a TECOPHILIC® material 2104,an opening 2106 providing a pore that allows moisture to penetrate fromthe tissue to the patch, an elastomer cap 2018, a sensing coil 2110(first inductor structure) to detection hydration level of TECOPHILIC®layer 2104.

The example apparatus of FIG. 22 shows a quarter of sensing patch 2200that includes a shielding mesh 2112 below the TECOPHILIC® layer, so thatthe coil detects only moisture in the TECOPHILIC® layer and not in theskin.

The example apparatus of FIG. 23 shows a quarter of sensing patch 2300that includes both top shielding 2114 and bottom shielding 2112 toprovide electromagnetic isolation of the sensing coil 2110. A secondcoil 2116 is used for communication of the tissue condition measurementmade using the sensing coil 2110.

Ultrasound-Based Measurements

Sweat analysis, blood analysis, and muscular ultrasound analysis aspotential ways of monitoring hydration. Sweat analysis (via ionicconcentration analysis) and blood analysis (via hemoglobinconcentration) both presented practical issues in non-invasive samplecollection as well as the scalability of the necessary components.Ultrasound velocity to determine tissue hydration level as an indicatorfor overall hydration level utilizes a relationship proven by researchand is a method with minimal potential for complication.

FIG. 24 shows a cross-section of an example ultrasound system 2400 thatcan be used in conjunction with a capacitance-based system and/or aninductance-based system described herein to provide data indicative ofthe electrical properties of the tissue. Example ultrasound system 2400includes a piezoelectric crystal 2402, a hard polymer focusing element2404, a metal plate 2406, and the wiring 2408 to supply a voltage to thepiezoelectric crystal 2402.

FIG. 25 shows an example operation of the example ultrasound system 2400when a voltage is applied. The alternating voltage causes a shape changein the piezoelectric crystal 2402, and the shape change helps togenerate the ultrasound waves.

FIG. 26A shows an example device mount 2600 about a bicep tissue. FIG.26B shows a cross-section of the device mount 2600 disposed about thebicep tissue 2602. The ultrasound system includes an ultrasoundgenerator 2604 and an ultrasound receiver 2606.

Using ultrasound velocity or tissue impedance to monitor hydration hasthe several specific advantages over blood and sweat analysis:

-   -   Blood and sweat analysis would likely require disposable,        adhesive sensor units and may be costly. An ultrasound device        can easily be designed to be reusable.    -   There are specific locations, including the thigh and upper        bicep (see FIG. 26A), at which ultrasound velocity assists in        hydration monitoring, and these locations are conducive to use        of a device during vigorous activity. The optimal locations for        a sweat or blood monitoring system might be harder to determine.    -   The ultrasonic device can be made non-invasive.

Non-limiting examples of benefits of the present disclosure include thefollowing:

-   -   The sensor circuitry is fully flexible, stretchable and        conformable for a more comfortable and portable user experience,        whether incorporated into an arm/leg band or a form-fitted        garment.    -   Hydration status readings will be derived using the average of        velocity readings taken from multiple transducer-sensor pairs        stationed in multiple arrays throughout the band. An increased        number of trials will help to increase the accuracy of the        readings. Additionally, the average reading will help mitigate        any inconsistencies caused by small potential changes in        transducer-sensor separation due to the conformal nature of the        band.    -   Hydration status may be viewed in real-time on the arm/leg band        or form-fitted clothing item via the included LED indicator        lights.    -   The arm/leg band may be wireless and transmit data to mobile        devices and portable music players.    -   Through innovative low-power management techniques the circuit        can operate on a very small power source.

An RF inductor coil may be fabricated on a flexible and/or stretchysubstrate that may be worn on the skin or integrated into form-fittedclothing. The state of hydration is determined by measuring the resonantfrequency of the coil. This frequency is related to the impedance of thetissue adjacent to the coil. Changes in resonant frequency may becorrelated with changes in impedance, which in turn reflects changes inthe state of hydration. The depth of tissue to which the coil issensitive to changes in impedance scales with the radius of the coil.Small coils (<1 cm) are designed to be sensitive primarily to thehydration of the skin while larger coils (>1 cm) are designed to besensitive to the state of hydration of muscle.

In various examples, these sensors—ultrasound and impedance(inductance-based and/or capacitance-based)—may be used alone or incombination. It is also contemplated that these sensors—ultrasound andimpedance (inductance-based and/or capacitance-based)—may be used incombination with other types of sensors that measure the composition ofsweat (e.g., sensors that measure conductivity or sensors that measurethe concentration of selective ions such as sodium potassium andcalcium, and others).

Example components are the ultrasonic transducer/receiver arraycircuits. The ultrasonic transducers and receivers are piezoelectricdisc actuators laid into a circuit with a series of analog-to-digitalconverters (ADCs) that process the signals from the transducer-receiverpairs.

These transducer/receiver circuits are laid into the sleeve of at-shirt, the leg of a pair of compression shorts, or a sport armband orlegband made of a formfitted, flexible, stretchable material such asneoprene, spandex or other types of polymer materials. One exemplaryconfiguration is three or more arrays of transducers and receiversspaced equidistant from each other. Each section contains twotransducers and two receivers. Each transducer is responsible forcommunicating with a receiver in an adjacent array and vice versa. Thetransducer-receiver sections do not communicate with diagonal sectionsdue to bone interference, only adjacent sections.

Hydration status is monitored based upon the velocity of ultrasoundwaves through the muscular tissue. There is a proven linearproportionality between tissue hydration level and the velocity ofultrasonic waves through the tissue (Topchyan, et al. Ultrasonics 44,2006, 259-264). As the muscle tissue becomes more dehydrated, ultrasoundvelocity will become faster. This linear relationship does not hold atextreme levels of dehydration. The ADCs within the circuits measure thetime differential between the ultrasound signal propagation at thetransducer and signal reception at the receiver. This time differentialis then divided by the distance between the transducer and receiver toobtain an ultrasound velocity. This is measured at regular intervals. Inan example where these measurements are made every thirty seconds, oneoverall velocity will be calculated from an average of the readings fromeach of the eight transducer-receiver pairs. Each pair will be activatedonce during each thirty-second interval to retrieve a velocity reading,and only one pair will be activated at a time to eliminate anypossibilities of constructive or destructive interference.

Example Systems for Using Apparatus for Measuring Tissue Properties

In an non-limiting example, an apparatus or system according to any ofthe principles described herein can be mounted to the tissue as a partof a patch. An example of a patch 2702 that can include at least one ofany of the apparatus described herein is shown in FIG. 27. The patch2702 may be applied to tissue, such as skin. A handheld device 2704 canbe used to read the data in connection with the electrical measurementperformed by the apparatus of the patch 2702. For example, the patch2702 can include a transmitter or transceiver to transmit a signal tothe handheld device 2704. The data in connection with the electricalmeasurement can be analyzed by a processor of the handheld device 2702to provide the indication of the tissue condition according to theprinciples described herein.

As shown in FIG. 27, the patch may be used in connection with asubstance 2706 that is applied to the tissue. The substance 2706 may beconfigured to change the condition of the tissue, including treating adisease of the tissue. For example, the substance 2706 may be configuredto be applied to the skin tissue to provide protection against the UV.In this example, the apparatus of the patch would be configured toperform electrical measurements to provide an indication of UV and/orSPF sensing on the tissue, to prevent sun damage and/or to recommendprotective products. In another example, the substance 2706 may beconfigured to be applied to the tissue to treat a disease or othermalformation of the tissue.

In an example, the patch 2702 may be a disposable adhesive patch that isconfigured for comfort and breathability.

In another example, the patch 2702 may be a more durable sensor patchthat is configured for comfort and long-term wear. The sensor patch mayinclude onboard sensors to measure the tissue condition of interest, amemory to log the data in connection with the electrical communication,and a near-field communication device that allows a scan of the sensorpatch with a handheld device to perform a status check and download.Non-limiting examples of the handheld device include a smartphone,tablet, slate, an e-reader or other handheld computing device. Thesensor patch may include an energy storage device, such as a battery, toprovide the voltage potential used for performing the measurements asdescribed hereinabove.

In an example, the system may include the patch 2702 and a charging pad(not shown). The patch 2702 may be placed on the charging pad to chargethe energy storage component of the patch 2702. The charging pad may becharged in an AC wall socket. The charging pad may be an inductivecharging pad.

In an example implementation, the patch 2702 can include an apparatusfor performing SPF monitoring based on the electrical information from acapacitance-based and/or an inductance-based measurement. The exampleapparatus according to this implementation can include an onboard UVAand/or UVB sensor. The tissue condition that is reported is the sunprotection effectiveness of a sunscreen product for protection of thetissue. An example disposable patch according to this implementation canprovide a surface that is engineered to simulate skin wetting propertiesto, accurately represent sunscreen distribution.

The example SPF monitoring system can use a durable sensor patch alongwith disposable adhesive patches. In an example method for use of theSPF monitoring system, the patch 2702 can be placed in a discreethigh-exposure location on a person's body if extended sun exposure isexpected. Over time, e.g., throughout the day, a NFC-enabled handhelddevice can be placed in proximity to the patch 2702 to check how muchsun protection still remains. The handheld device can include anapplication (an App) to log and track “SPF state.” That is, the App onthe handheld device can include machine-readable instructions such thata processor unit of the handheld device analyzes the electricalmeasurements from the apparatus of the patch 2702 and provides theindication of the tissue status (SPF state) based on the analysis. TheApp can include machine-readable instructions to provide (i) productrecommendations, (ii) suggestions to re-apply a product, or (iii)present an interface that facilitates the purchase of, or obtaining asample of, recommended products. After use, such as at the end of theday, a consumer may dispose of the Adhesive patch, and retain the sensorpatch reuse at a later time. The sensor patch can be re-charged using acharging pad as described herein.

In another example implementation, the patch 2702 can include anapparatus to perform as a UV dosimeter based on the electricalinformation from a capacitance-based and/or an inductance-basedmeasurement. The example apparatus according to this implementation caninclude an onboard UVA and/or UVB sensor. The tissue condition that isreported is the UV dosage exposure of an individual.

The example UV dosimeter system can use a durable sensor patch alongwith disposable adhesive patches. In an example method for use of the UVdosimeter system, the patch 2702 can be placed in a discreethigh-exposure location on a person's body if extended sun exposure isexpected. Over time, e.g., throughout the day, a NFC-enabled handhelddevice can be brought in proximity to the Adhesive patch to downloadlogged data, gathered throughout use of the patch 2702. The App can beused to track “personal sun exposure state.” That is, the App on thehandheld device can include machine-readable instructions such that aprocessor unit of the handheld device analyzes the electricalmeasurements from the apparatus of the patch 2702 and provides theindication of the tissue status (personal sun exposure state) based onthe analysis. The App can include machine-readable instructions toprovide and can provide (i) product recommendations, (ii) suggestions tore-apply products, or (iii) present an interface that facilitates thepurchase of, or obtaining a sample of, recommended products. After use,such as at the end of the day, the individual may dispose of theAdhesive patch, and retain the sensor patch for reuse at a later time.The sensor patch can be re-charged on charging pad, e.g., overnight.

In another example implementation, the patch 2702 can include anapparatus to perform as a hydration and/or firmness monitor based on theelectrical information from a capacitance-based and/or aninductance-based measurement. The example apparatus according to thisimplementation can include an onboard hydration sensor. The tissuecondition that is reported is the tissue hydration and/or firmness of anindividual. Based on the indication, the patch 2702 can performdiagnosis and recommendation for personalized skin hydration andfirmness product treatments.

The example hydration and/or firmness monitoring system can use adurable sensor patch along with disposable adhesive patches. In anexample method for use of the hydration and/or firmness monitoringsystem, the individual may create a personal profile and affiliate aproduct choice with that profile on a handheld device. An App that canbe used to generate the profile may be downloaded to the handhelddevice. After application of a product, e.g., at night, an individualmay place one or more patches 2702 on an area of interest on the body.The individual may bring the NFC-enabled handheld device in proximity tothe patch(es) 2702 to download data gathered intermittently during useof the patch(es) 2702. The App can include machine-readable instructionsto track “personal hydration and firmness states.” In another example,the App can include machine-readable instructions to provide (i) productrecommendations, (ii) suggestions to re-apply products, or (iii) presentan interface that facilitates purchase of, or obtaining a sample of,recommended products. The individual may repeat the procedure withvarying products and beauty routines and update the profile based on theresults.

Systems for Indicating and/or Transmitting Measurements

In one example implementation, the status of the tissue condition(including hydration status) may be monitored with a series of LEDindicator lights. That is, the LED lights can be used according of anyof the examples described herein to provide the indication of the tissuecondition.

As one example of many ways to illustrate the value or the change invalue of tissue condition (including hydration levels), LED indicatorlights may be lit to indicate the percent change in sensor measurementfrom the initial reading. The LEDs are grouped in pairs which light uptogether depending upon hydration level as displayed in the table below:

All LED indicators leading up to the specific measurement change canremain lit, but they may go off if/when the subject rehydrates. Forexample, at a 4% change in a measurement, two green pairs and one yellowpair of LEDs may be lit. If that increase drops to 0.5%, only one greenpair may be lit.

This is one example of many ways in which indication of hydration levelmay be presented to the user. Numerical seven-segment LED or LCDdisplays can also be used to provide numerical or percentage values.Linear arrangements of LEDs can ‘chart’ hydration levels where longerruns of illuminated LEDs indicate greater hydration. Brightness levelcan also indicate hydration level or sequential patterns or other manyways to indicate increasing, decreasing or absolute values of hydrationlevels may be displayed and made integral to the unit.

In yet other implementations, rather than employing external powersources, “on-board” power sources may be employed. In one instantiation,the power source may be a small 12V battery contained in rigid housing.Such power management techniques can use a variety of well-known batteryand energy storage management methods.

In another aspect, data transmissions to a cellular phone, portablemusic player, such as an mp3 player, or other mobile device in order maybe supported to allow for data logging and audible hydration statusalerts via an accompanying software application. In one example,processing circuitry as well as a Bluetooth data transmitter (or otherwireless techniques such as WiFi (802.11 protocols), ANT or otherwireless means and protocols) are employed to facilitate suchtransmission.

In yet another aspect, the LED light indicator system may be replaced orsupplemented by other indication mechanisms. For example, the LED lightindicator system may be replaced by a display which gives a precise readout of the percent change in sensor measurement from a previouslymeasured baseline, and therefore of the percent change in hydrationlevel. Another solution is to remove on-board indication and requireintegration with a mobile device or mp3 player. This takes advantage ofprocessing power that is available within the phone or other mobiledevice and reduce or eliminate processing resources on the sport band.

According to other examples, hydration monitoring apparatus may includea thin, flexible and/or stretchable capacitance-based sensor on aconformal substrate. The sensor electrode is a passive device and isapplied to the skin in a variety of locations like a decal or temporarytattoo, or it may be integrated into form-fitted clothing. Thecapacitance-impedance between the conductive structures are measured andcorrelated with the state of hydration.

According to yet other examples, hydration monitoring apparatus mayinclude a thin, flexible and/or stretchable inductor structure (such asbut not limited to a RF inductor coil) on a conformal substrate. Thecoil is a passive device and is applied to the skin in a variety oflocations like a decal or temporary tattoo, or it may be integrated intoform-fitted clothing. The coil needs can be placed near the skin anddoes not have to be direct contact. The resonance frequency of the coilis then measured and correlated with the state of hydration.

Such information about tissue condition (including hydration) may bestored, transmitted and recorded to tie into other health informationfrom a particular activity or series of activities to give a long termprofile of body hydration over time. This information may be furtheredintegrated into other health related information over time and presentedto the user, parent, doctor, coach or other interested party, in asoftware application or in web-based tools, to give graphical and visualinformation of status over time. This may be used to spot trends andprovide early diagnosis of issues related to hydration and otherphysiological signs.

The information can also be used in ways to automatically update suchhealth status and information to social media sites and forums to allowfriends, fellow athletes and colleagues to compare and contrast similarinformation in a convenient form. Additional features would allowcomments and other communication in an online fashion to providecompetitive information and entertainment.

The apparatus is applied to locations where skin or muscle hydration isto be monitored. A baseline reading is taken at the beginning of anactive period, and then measurements are taken periodically. Changes inthe electrical information from the measurement can be correlated withchanges in tissue condition, such as but not limited to hydration state.

Specific activity may be tied to specific changes in the hydrationstate, such as changes in level of activity, drinking more water, orother fluids such as a sport drink, or applying certain creams orlotions that change the hydration level of the skin.

For apparatus that include components for measuring based on ultrasoundtechniques, the apparatus may be wrapped around the user's upper arm(the biceps/triceps area), as illustrated in FIG. 26A, or lower leg (thecalf) and secured using means such as, but not limited to, adhesives orhook-and-loop style fasteners (commercially available as VELCRO®)components. The apparatus is then powered on and a baseline ultrasoundvelocity reading is taken before activity begins. The apparatus may beused regardless of clothing or other equipment used, so long as theapparatus has direct contact with the skin.

Hydration Monitoring

Various examples of the present disclosure provide a direct, specifictargeting of the use case for the hydration monitor. The specificmedical applications can be broad, but specifically this can have anapplication for wound healing, rehabilitation, detoxification, andmonitoring while in and out of the hospital for hydration levels.

With wound healing and physical rehabilitation, dehydration can resultin diminished healing ability since water is a major component ofhealthy cells. A large, exposed wound—or even a draining wound—may alsoexude a large amount of fluids, resulting in dehydration and electrolyteimbalance. Maintaining body cell mass helps promote wound healing. Thebody enters a type of hypermetabolic state during wound healing as anincrease of 10-50% of energy expenditure is common during the repair andrecovery process. This hypermetabolic state can lead to dehydration, anddehydration can then affect the breakdown of proteins that areabsolutely crucial in the healing process, as water aids the body innutrient absorption and deployment. Hydration plays a role in woundhealing as dehydrated skin is less elastic, more fragile and moresusceptible to breakdown. Dehydration can also reduce efficiency ofblood circulation, which can impair the supply of oxygen and nutrientsto the wound. Water and hydration play a massive role in the healingprocess.

During the detoxification process, hydration plays a role in the body'sfunction to excrete toxins and waste. Hydration is the foundation fordetoxification based on a flow of water in and out of the cells. pHbalance in the body is dependent on detoxification of built up toxinsinside the cells. Water and hydration plays a role in this process, andit has been shown that people do not drink enough water on a daily basisto maintain an optimal level of hydration that rids the body of toxinsand provides an overall health and wellness well being. Those who havelived for many years without proper water intake are the most likely tosuccumb to the buildup of toxins in the body. It is difficult to performaccurate monitoring of the level of tissue hydration on a day-to-daybasis—other than the crude method of comparing colors of urine. Thishydration monitor can provide a way for people to lead a healthier lifethrough all of the benefits of hydration (signs of dehydration rangefrom drops in physical and mental performance, migraines, muscle aches,and constipation, to even more severe episodes requiringhospitalization).

Monitoring patients (even self-monitoring) while in and out of thehospital for hydration levels can be beneficial when considering theextremely dehydrating effects of painkillers and antibiotics. Just as inwound healing above, the body has an increased need for hydration whiletaking painkillers and antibiotics. Many painkillers and manyantibiotics have a dehydrating effect on the body, thus making itdifficult to recover from injury. Painkillers have a double effect, theyuse a large amount of cellular water to be processed, and they also mutethe body's natural response to dehydration; thirst. The process ofprogressive cellular dehydration can occur over time. Also, manyantibiotics cause diarrhea, which can cause severe dehydration overtime. Monitoring levels of dehydration is both preventative andpro-active in this setting.

There is also an application for the weight-loss market for thehydration monitor. Staying hydrated is very important in generalhealth/well-being from day-to-day (focus benefits, short-term health,long-term health, etc.) but it has been well-documented that far toomany people just do not drink enough water throughout the day and candevelop dehydration that can be chronic. The diet and/or athleticsindustry may derive great benefit by using hydration as a way to manageappetite, leading to healthy weight loss and a healthy life style at avery low-cost with no side effects. Water is a form of hydration that isreadily available and very inexpensive. It has long been known thatwater is the essential key to weight loss by suppressing appetite (the“full-feeling”, reducing caloric intake when properly hydrated, etc.),boosting metabolism, and increasing energy production. Hydration studieshave shown that dehydration can affect both mood and willpower: a poormood and willpower makes you much more likely to eat food high in fat,sugar and calories. Proper hydration brings an absolute huge shift inthe diet/fitness market, and the monitors described herein facilitatethat. In non-limiting example implementation, the apparatus is used as ahydration monitor.

The data provided by an apparatus or system herein, in performing acapacitance-based or an inductance-based measurement, can be used todetermine the timing of replacing body fluids. Not replacing enoughfluids and electrolytes lost can lead to severe cramping, drop-off inathletic performance, and mental confusion that can be traced to thechanges at cellular level upon dehydration. Replacing too much fluidsand electrolytes can lead to an electrolyte imbalance andgastrointestinal problems, not to mention a bloated, full feeling whilein competition or training. Changes in temperature, humidity, altitude,level of activity and the degree of heat acclimation the athlete orsoldier has further complicates the process. Measuring the loss offluids from the skin can be a reliable way to measure dehydration ormore generally the state of hydration in real-time.

The apparatus and systems described herein can provide a real-time proxyfor total volume of sweat lost in aworkout/practice/game/battle/training or any specified period of timefrom when the monitor is placed on the body. Thus, the issue ofreplacing fluids lost is made simpler; replace what is lost in real-timeduring the activity, training or battle, thus assisting to reduce orsubstantially eliminate avoiding the drop-off in performance mentallyand physically.

CONCLUSION

All literature and similar material cited in this application,including, but not limited to, patents, patent applications, articles,books, treatises, and web pages, regardless of the format of suchliterature and similar materials, are expressly incorporated byreference in their entirety. In the event that one or more of theincorporated literature and similar materials differs from orcontradicts this application, including but not limited to definedterms, term usage, described techniques, or the like, this applicationcontrols.

The section headings used herein are for organizational purposes onlyand are not to be construed as limiting the subject matter described inany way.

While various examples have been described and illustrated herein, thoseof ordinary skill in the art will readily envision a variety of othermeans and/or structures for performing the function and/or obtaining theresults and/or one or more of the advantages described herein, and eachof such variations and/or modifications is deemed to be within the scopeof the examples described herein. More generally, those skilled in theart will readily appreciate that all parameters, dimensions, materials,and configurations described herein are meant to be exemplary and thatthe actual parameters, dimensions, materials, and/or configurations willdepend upon the specific application or applications for which theteachings is/are used. Those skilled in the art will recognize, or beable to ascertain using no more than routine measurementation, manyequivalents to the specific examples described herein. It is, therefore,to be understood that the foregoing examples are presented by way ofexample only and that, within the scope of the appended claims andequivalents thereto, examples may be practiced otherwise than asspecifically described and claimed. examples of the present disclosureare directed to each individual feature, system, article, material, kit,and/or method described herein. In addition, any combination of two ormore such features, systems, articles, materials, kits, and/or methods,if such features, systems, articles, materials, kits, and/or methods arenot mutually inconsistent, is included within the scope of the presentdisclosure.

The above-described examples of the invention can be implemented in anyof numerous ways. For example, some examples may be implemented usinghardware, software or a combination thereof. When any aspect of anexample is implemented at least in part in software, the software codecan be executed on any suitable processor or collection of processors,whether provided in a single device or computer or distributed amongmultiple devices/computers.

In this respect, various aspects of the invention, may be embodied atleast in part as a computer readable storage medium (or multiplecomputer readable storage media) (e.g., a computer memory, one or morefloppy discs, compact discs, optical discs, magnetic tapes, flashmemories, circuit configurations in Field Programmable Gate Arrays orother semiconductor devices, or other tangible computer storage mediumor non-transitory medium) encoded with one or more programs that, whenexecuted on one or more computers or other processors, perform methodsthat implement the various examples of the technology discussed above.The computer readable medium or media can be transportable, such thatthe program or programs stored thereon can be loaded onto one or moredifferent computers or other processors to implement various aspects ofthe present technology as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of the present technology asdiscussed above. Additionally, it should be appreciated that accordingto one aspect of this example, one or more computer programs that whenexecuted perform methods of the present technology need not reside on asingle computer or processor, but may be distributed in a modularfashion amongst a number of different computers or processors toimplement various aspects of the present technology.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various examples.

Also, the technology described herein may be embodied as a method, ofwhich at least one example has been provided. The acts performed as partof the method may be ordered in any suitable way. Accordingly, examplesmay be constructed in which acts are performed in an order differentthan illustrated, which may include performing some acts simultaneously,even though shown as sequential acts in illustrative examples.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one example, to A only (optionally including elements other than B);in another example, to B only (optionally including elements other thanA); in yet another example, to both A and B (optionally including otherelements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one example, to at least one, optionally including more thanone, A, with no B present (and optionally including elements other thanB); in another example, to at least one, optionally including more thanone, B, with no A present (and optionally including elements other thanA); in yet another example, to at least one, optionally including morethan one, A, and at least one, optionally including more than one, B(and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

The claims should not be read as limited to the described order orelements unless stated to that effect. It should be understood thatvarious changes in form and detail may be made by one of ordinary skillin the art without departing from the spirit and scope of the appendedclaims. All examples that come within the spirit and scope of thefollowing claims and equivalents thereto are claimed.

1-66. (canceled)
 67. An apparatus for monitoring a condition of atissue, the apparatus comprising: a substrate disposed above the tissue,wherein the substrate is formed from a material that changes a statewith a change in the condition of the tissue; and at least one firstinductor structure disposed above the substrate, wherein at least one ofan electrical property and a physical property of the at least one firstinductor structure changes with a change in the condition of thesubstrate, and wherein a measure of the electrical property or thephysical property of the at least one first inductor structure providesan indication of the condition of the tissue.
 68. The apparatus of claim67, wherein the condition of the tissue is a hydration state of thetissue, a volume of sweat lost, a mechanical property of the tissue, adisease state of the tissue, or a level of SPF protection of the tissue.69. The apparatus of claim 67, wherein the first inductor structure is aspiral coil structure, a cylindrical coil structure, or a toroidalstructure.
 70. The apparatus of claim 67, further comprising a reader,wherein the reader comprises at least one second inductor structure,wherein a measure of a change in an electrical property of the at leastone second inductor structure brought in proximity to the at least onefirst inductor structure provides the measure of the electrical propertyof the at least one first inductor structure.
 71. The apparatus of claim67, wherein the second inductor structure is the same configuration asthe first inductor structure.
 72. The apparatus of claim 67, wherein thefirst inductor structure and the second inductor structure are a spiralcoil structure, a cylindrical coil structure, or a toroidal structure.73. The apparatus of claim 67, wherein the electrical property is amagnetic flux density from the at least one first inductor structure.74. The apparatus of claim 67, further comprising an encapsulation layerdisposed over at least a portion of the at least one first inductorstructure.
 75. The apparatus of claim 74, wherein the encapsulationlayer is a polymer.
 76. The apparatus of claim 75, wherein the portionsof the polymer comprise an adhesive, and wherein the adhesive attachesthe portions of the polymer to the tissue.
 77. The apparatus of claim67, further comprising a separator layer disposed between the at leastone inductor structure and the substrate, wherein the separator layer isa non-conductive material.
 78. The apparatus of claim 77, wherein theseparator layer is formed from a polymer.
 79. The apparatus of claim 67,further comprising an ultrasound apparatus, and wherein the ultrasoundapparatus provides a measure of an electrical property of the tissue.80. The apparatus of claim 79, wherein the ultrasound an apparatuscomprises: an ultrasound generator disposed proximate to a first portionof the tissue of interest, wherein the ultrasound generator comprises apiezoelectric crystal, wherein the ultrasound generator directsultrasound waves at a portion of the tissue; and an ultrasound receiverdisposed proximate to a second portion of the tissue of interest that isdifferent from the first portion, wherein the ultrasound receiverprovides a measure of ultrasound waves arriving at the second portion ofthe tissue, and wherein the measure of ultrasound waves arriving at thesecond portion of the tissue provides an indication of the condition ofthe tissue.
 81. A system for monitoring a condition of a tissue,comprising: at least one apparatus of claim 67; and at least one othercomponent, wherein the at least one other component is at least one of abattery, a transmitter, a transceiver, a memory, a radio-frequencyidentification (RFID) chip, a processing unit, an analog sensing block,a UVA sensor, a UVB sensor, and a temperature sensor.
 82. A method formonitoring a condition of a tissue, the method comprising: receivingdata indicative of an electrical measurement of the tissue, wherein theelectrical measurement is performed using at least one apparatus of 67;and analyzing the data using at least one processor unit, wherein theanalysis provides an indication of the condition of the tissue.
 83. Themethod of claim 82, wherein the analyzing the data comprises applying aneffective circuit model to the data, and wherein a value of a parameterof the model provides the indication of the condition of the tissue. 84.The method of claim 82, wherein the analyzing the data comprisescomparing the data to a calibration standard, and wherein the comparingprovides the indication of the condition of the tissue.
 85. The methodof claim 84, wherein the calibration standard comprises a correlationbetween values of electrical measurement and the indication of thecondition of the tissue.